Users are people who are interested in and have access to the content that you post for free. As soon as they start paying for your content, they become your subscribers.
This page lets you see the access rights that are assigned by default to your users and that you can change as you see fit. You can see whether and who of your users has requested any additional users rights. You can also invite users to join your app by inputting either their username or their email.
At the bottom of the screen, you can have the overview of all users who have access to your app together with the access rights to your content that they enjoy.