In the Contacts section you will see all the current users on the website. You can filter them by groups or add a new one manually from the Add Member button.
If you click on the member you will open their profile page.
For each member you have their name, email and any contact properties that you have in your Engage section. You can manage those from the Settings -> Properties. You can also reset the password or delete the user.
You can modify each member/contact by clicking on their name:
If they have subscriptions, you will see a subscription tab next to the Orders.