Relay vs Lobby

Relay and Lobby are two distinct Unity services that you can use together to create a peer-hosted game with an embedded Lobby. However, due to some functionality overlap between the services, it’s important to note the distinctions.

Lobby facilitates grouping of players and configuration settings before they enter a game session while Relay facilitates a multiplayer game session without a dedicated game server or the complications of direct peer-to-peer networking. Use Lobby and Relay together to create a game with a lobby that facilitates multiplayer game sessions without dedicated game servers.

Relay	Lobby
Relay is a networking solution that connects players in a peer-to-peer fashion using a server-client environment.	Lobby facilitates grouping players and configuration settings before game sessions.
Relay facilitates a multiplayer game session without a dedicated game server (DGS) or the complications of direct peer-to-peer connections.	Lobby isn’t limited to peer-to-peer (P2P) sessions or use with Relay. You can also use Lobby with a traditional multiplayer game with a dedicated game server (DGS).