Peergos users can send follow requests to each other. If accepted, the other user can then share files or send messages with you. Following is a one-way mechanism: If Agata follows Bartek then Bartek can share files with Agata. If Bartek is also following Agata, then she can also share files with Bartek. Following can be revoked by either user at any point.
Your friend list is kept encrypted in your own Peergos space, hidden from other users and the server.
There is also a secret link mechanism for sharing files with people who do not have peergos accounts.