# Amazon GameLift Servers key terms This topic provides definitions for key technical terms used in Amazon GameLift Servers documentation and services. **Active game session** A game session that is currently running and accepting or hosting players. Used as a metric to monitor fleet utilization and capacity planning. See [Monitor Amazon GameLift Servers with Amazon CloudWatch](monitoring-cloudwatch.md). **Alias** A friendly identifier for a fleet that provides an abstraction layer between your game client and fleet resources. Aliases allow you to update fleet configurations without changing your game client code. See [Abstract an Amazon GameLift Servers fleet designation with an alias](aliases-intro.md). **AMI (Amazon Machine Image)** A pre-configured virtual machine image used to create Amazon EC2 instances for managed fleets. Contains the operating system, runtime libraries, and Amazon GameLift Servers agent software needed to run game servers. See [Amazon GameLift Servers managed EC2 fleets](fleets-intro-managed.md). **Anywhere fleet** A type of fleet that uses customer-provided compute resources managed outside of Amazon GameLift Servers. Anywhere fleets allow you to integrate existing infrastructure or hybrid cloud solutions with Amazon GameLift Servers game session management. See [Amazon GameLift Servers Anywhere fleets](fleets-intro-anywhere.md). **Authentication token** A security credential generated by Amazon GameLift Servers that authenticates game server processes running on Anywhere compute resources. Required for server processes to communicate with the Amazon GameLift Servers service. See [Amazon GameLift Servers Anywhere fleets](fleets-intro-anywhere.md). **Backend service** A coordination layer between game clients and the Amazon GameLift Servers service that controls communication for game session placement requests and retrieves game session information. Acts as a secure intermediary to protect hosting resources from malicious attacks. See [How hosting with Amazon GameLift Servers works](gamelift-howitworks.md). **Game server build** A packaged version of your game server software that includes all files needed to run your game server on Amazon GameLift Servers hosting resources. Contains the game server executable, dependencies, and assets. See [Package a game server build for deployment](gamelift-build-intro.md). **Compute** In container fleets, represents a copy of a game server container group on a fleet instance. Each compute can host one game session at a time. See [How containers work in Amazon GameLift Servers](containers-howitworks.md). **Container fleet** A type of managed fleet that runs containerized game servers using container images instead of traditional builds. Provides flexibility for deploying game servers with specific runtime environments and dependencies. See [Amazon GameLift Servers managed container fleets](fleets-intro-containers.md). **Container group** A collection of containers that work together to provide game server functionality. Similar to a container task or pod, defining how containers behave, dependencies, and resource sharing within a container fleet. See [How containers work in Amazon GameLift Servers](containers-howitworks.md). **Destination** In game session queues, a fleet or alias that can receive game session placement requests. Queues can have multiple destinations with different priorities and latency policies. See [Customize a game session queue](queues-design.md). **Fleet** A collection of computing resources that run your game servers. Fleet resources can be distributed across multiple geographic locations and each resource runs one or more game server processes. See [Deploy hosting fleets for Amazon GameLift Servers](fleets-intro.md). **Fleet location** A specific AWS Region or Local Zone where fleet instances are deployed. Multi-location fleets can span multiple locations to reduce latency and improve availability. See [Deploy hosting fleets for Amazon GameLift Servers](fleets-intro.md). **FlexMatch** Amazon GameLift Servers matchmaking service that automatically forms player matches based on configurable rules and requests game session placement for completed matches. Supports skill-based matching, team balancing, and match backfilling. See [What is GameLift FlexMatch?](https://docs.aws.amazon.com/gameliftservers/latest/flexmatchguide/match-intro.html) **Game client** Your game software that runs on a player's device. Initiates player placement into game sessions by communicating with a backend service and connects directly to game servers for gameplay. See [How hosting with Amazon GameLift Servers works](gamelift-howitworks.md). **Game property** Key-value pairs of custom data associated with a game session. Used to pass configuration information, game rules, or other metadata to game servers and clients. See [GameProperty](https://docs.aws.amazon.com/gameliftservers/latest/apireference/API_GameProperty.html) in the API Reference. **Game server** Your custom server software that manages game state, processes player actions, and synchronizes gameplay across multiple connected players. Integrates with the Amazon GameLift Servers Server SDK to communicate with the service. See [Add Amazon GameLift Servers to your game server with the server SDK](gamelift-sdk-server-api.md). **Game server activation** The process of starting and initializing a game server process on a hosting resource. Includes loading the game server executable, establishing communication with Amazon GameLift Servers, and preparing to host game sessions. See [Add Amazon GameLift Servers to your game server with the server SDK](gamelift-sdk-server-api.md). **Game server container** A container within a game server container group that runs the game server application. Automatically designated as essential to the container group lifecycle. See [How containers work in Amazon GameLift Servers](containers-howitworks.md). **Game server container group** A type of container group that manages containers running game server applications and supporting software. Required for container fleets to host game sessions and can be replicated across fleet instances. See [How containers work in Amazon GameLift Servers](containers-howitworks.md). **Game server process** A running instance of your game server executable on a hosting resource. Each process can host one game session at a time and communicates directly with Amazon GameLift Servers to report status and receive instructions. See [Add Amazon GameLift Servers to your game server with the server SDK](gamelift-sdk-server-api.md). **Game session** An instance of your multiplayer game running on a game server process. Represents a single gameplay experience that multiple players can join and participate in together. See [How hosting with Amazon GameLift Servers works](gamelift-howitworks.md) and [GameSession](https://docs.aws.amazon.com/gameliftservers/latest/apireference/API_GameSession.html) in the API Reference. **Game session data** Information associated with a game session including player data, game state, session properties, and other runtime information used by game servers and clients. See [GameSession](https://docs.aws.amazon.com/gameliftservers/latest/apireference/API_GameSession.html) in the API Reference. **Game session placement** The process of locating available game servers to host new game sessions. Uses real-time information about game server availability to make optimal placement decisions based on factors like cost and latency. See [Integrate Amazon GameLift Servers game client functionality](gamelift-sdk-client-api.md) and [StartGameSessionPlacement](https://docs.aws.amazon.com/gameliftservers/latest/apireference/API_StartGameSessionPlacement.html) in the API Reference. **Game session protection** A setting that prevents Amazon GameLift Servers from terminating game server processes that are hosting active game sessions during scaling events or fleet updates. Ensures ongoing games are not interrupted. See [Manually set capacity for an Amazon GameLift Servers fleet](fleets-updating-capacity.md). **Game session queue** A placement mechanism that uses configurable algorithms to place game sessions for optimal outcomes. Can prioritize placements based on factors such as lowest hosting cost and lowest player latency across multiple geographic locations. See [Configure game session placement](queues-intro.md). **Idle instance** A fleet instance that is running but not currently hosting any active game sessions. Used as a metric for monitoring fleet efficiency and scaling decisions. See [Monitor Amazon GameLift Servers with Amazon CloudWatch](monitoring-cloudwatch.md). **Inbound permissions** Network access rules that define which IP addresses and port ranges can be used to connect to fleet instances. Controls access to game servers and ensures secure connections. Both managed EC2 and managed container fleets require inbound permissions configuration. See [IpPermision](https://docs.aws.amazon.com/gameliftservers/latest/apireference/API_IpPermission.html) and [Configure network connections](containers-design-fleet.md#containers-custom-network). **Latency policy** Rules in game session queues that define acceptable latency thresholds for player connections. Used to ensure players are placed in game sessions with acceptable network performance. See [Customize a game session queue](queues-design.md). **Managed fleet** A type of fleet where Amazon GameLift Servers deploys and manages computing resources in the AWS Cloud. Provides automatic scaling, health monitoring, and infrastructure management. See [Amazon GameLift Servers managed EC2 fleets](fleets-intro-managed.md). **Matchmaking** The process of grouping players together for multiplayer gameplay based on criteria such as skill level, latency, or other game-specific factors. In Amazon GameLift Servers, primarily handled by FlexMatch. See [What is GameLift FlexMatch?](https://docs.aws.amazon.com/gameliftservers/latest/flexmatchguide/match-intro.html) **Metric group** A collection of related performance metrics used for monitoring and auto-scaling decisions. Groups metrics like active game sessions, available game servers, and player utilization. See [Auto-scale fleet capacity with Amazon GameLift Servers](fleets-autoscaling.md). **Per-instance container group** An optional container group type that runs additional software on each fleet instance. Useful for background services or monitoring tools, with only one copy deployed per instance. See [How containers work in Amazon GameLift Servers](containers-howitworks.md). **Player session** A connection slot for a player in a game session. Used to reserve game session slots, validate players when they connect, and track player connection status and disconnects. See [Integrate Amazon GameLift Servers game client functionality](gamelift-sdk-client-api.md) and [PlayerSession](https://docs.aws.amazon.com/gameliftservers/latest/apireference/API_PlayerSession.html) in the API Reference. **Priority configuration** Settings that customize the prioritization order of a game session queue when selecting destinations for game session placement. Defines the overall queue behavior, in contrast to priority override lists which modify priority for individual placement requests. See [Prioritize game session placement](queues-design-priority.md). **Priority override list** An alternate priority list of locations that can be included in a game session placement request. Effectively replaces the queue's configured prioritization for locations for that one request only, without impacting other requests. See [Prioritize game session placement](queues-design-priority.md). **Process manager** A component that manages the lifecycle of multiple game server processes within a container or instance. Handles starting, stopping, and monitoring individual game server processes. See [Optimize game server runtime configuration on managed Amazon GameLift Servers](fleets-multiprocess.md). **Realtime script** JavaScript code that defines game logic for Amazon GameLift Servers Realtime Servers. Handles player connections, message routing, and game state management without requiring a custom game server. See [What is Amazon GameLift Realtime Servers?](https://docs.aws.amazon.com/gameliftservers/latest/realtimeguide/realtime-intro.html) **Routing strategy** Configuration that determines how aliases direct traffic to fleets. Can route to a specific fleet or distribute traffic across multiple fleets based on defined rules. See [Abstract an Amazon GameLift Servers fleet designation with an alias](aliases-intro.md). **Runtime configuration** Settings that define how game server processes run on fleet instances, including the number of concurrent processes, launch parameters, and resource allocation. See [Optimize game server runtime configuration on managed Amazon GameLift Servers](fleets-multiprocess.md). **Scaling** The process of adjusting fleet capacity by adding or removing hosting resources based on player demand. Can be automatic (based on utilization metrics) or manual (administrator-controlled). See [Auto-scale fleet capacity with Amazon GameLift Servers](fleets-autoscaling.md). **Scaling policy** Rules that define when and how to automatically adjust fleet capacity. Can be target-based (maintain specific utilization) or rule-based (scale based on metric thresholds). See [Auto-scale fleet capacity with Amazon GameLift Servers](fleets-autoscaling.md). **Server SDK** Software development kit that provides the tools and libraries needed to integrate your game server with Amazon GameLift Servers. Enables communication between your game server and the service for session management, health reporting, and status updates. See [Add Amazon GameLift Servers to your game server with the server SDK](gamelift-sdk-server-api.md). **Session-based multiplayer** A multiplayer game architecture where gameplay occurs within discrete, time-limited sessions. Each session has a defined start and end, with players joining and leaving as needed. See [How hosting with Amazon GameLift Servers works](gamelift-howitworks.md). **Spot instances** A type of Amazon EC2 instance that uses spare AWS capacity at reduced cost. Spot instances can be interrupted when AWS needs the capacity back, making them suitable for fault-tolerant game workloads. See [Build a queue for Spot Instances](spot-tasks.md). **TLS certificate** A digital certificate used to enable encrypted communication between game clients and servers. Required for TLS-enabled fleets to ensure secure data transmission. See [Create an Amazon GameLift Servers managed EC2 fleet](fleets-creating.md).