The Organisation page shows your team's seat usage and limits, broken down by seat type - full seats, Knowledge Hub seats, and guest seats - so you can see at a glance how much room you have before adding more people.
This is also where team membership itself is managed:
Inviting Team Members - bring colleagues into your workspace and assign their initial role.
Removing Team Members - revoke access and free up a seat.
Changing Team Member Permissions - update someone's role and access level.