# Glossary

> Learn the terminology and key concepts used in the Unity Lobby documentation.

### UGS

Unity Gaming Services. The term used to refer to [Unity services](/services.md).

#### Host

A player who creates the lobby or assumes the role of host from another host.

#### Inactive lobby

Lobbies are marked as inactive if they haven’t been updated or sent a heartbeat request in the last 30 seconds. An inactive lobby can be reactivated by being updated or sending a heartbeat request. Inactive public lobbies do not appear in query results. A public or private lobby that has been inactive for more than one hour may be deleted at any time.

#### Lobby

The Multiplayer Services SDK uses lobbies as the underlying backend to store session data. When you create a session you also create a lobby.

#### Lobby data

Data specific to the lobby.

#### Lobby ID

Used when working directly with the Lobby SDK.

A randomly generated ID, or a string set with `CreateOrJoinLobbyAsync`, assigned to a lobby when it's created to uniquely identify it. When joining a public lobby, the lobby ID is used to identify the lobby to join.

#### Member data

Data that's only visible to players who have joined the lobby.

#### Player

A player within the lobby.

#### Player data

Data specific to the player in this lobby.

#### Private data

Data that is only visible to an individual player who is in the lobby.

#### Private lobby

A lobby that does not appear in query results and is generally only accessible using a lobby code.

#### Public data

Data that is visible to anyone, including players who are not in the lobby.

#### Public lobby

A type of lobby that is accessible to all players and appears in the query list.

#### Session

A session is a high-level abstration lever that manages the Lobby, Relay, and Matchmaker services. Sessions manage the entire multiplayer lifecycle by automatically combining Lobby, Relay, Matchmaker, and your networking library (Netcode) into a single unified system.

#### Session code

A randomly generated alphanumeric code or a string set by 'CreateOrJoinSessionAsync' that players can share with other players to join a private session (lobby). If the session code doesn't already exist a new session is created.

#### Query filter

A filter that can be provided as part of a query request to limit the results returned to lobbies that match specific properties.

#### Query list

A list of available public lobbies returned by a search query.

#### Quick Join

Players can use this to quickly find and join a lobby without having to manually select a specific lobby from a query list.

#### Relay

Unity Relay offers a way for game developers to securely provide increased connectivity between players by using a join code style workflow.