The Lobby is an official public world created by Cluster.
It is a perfect location to meet up with other users, much like a city square.
There are also world gate to recommended worlds, which you can use to world-hop with your friends.
How to enter the lobby
You can enter the lobby from here.
Alternatively, you can select the Lobby icon from the menu within Cluster by going to move (top right), and then selecting Lobby.