In Community you'll notice that there are two separate sections called Members and Users.
Each of those sections serve a different purpose:
A Member holds all memberships, billing information, bookings etc.
A User connects the Member to the members portal, e.g when you're enabling a member in order to grant them access to the members portal - more on that in this article - you're issuing permissions to their user that exists in the system.
You can see the different permissions that are being granted to Users depending on their Status in the system here.