Small enough to be noticed
A circle has a name, a member count and a conversation — not a feed, and not an audience.

Circles you create or join, a conversation that keeps going between them, and campaigns you pray through together.
A habit kept entirely in private is a habit with nobody to notice it, and most of them quietly stop. Not for lack of conviction — for lack of anyone expecting you.
Circles are small enough that your absence is noticed and your answer is celebrated.
Start a circle or join one. Inside is a conversation with replies and reactions, so a prayer request does not vanish under the next message and an answer can be pinned to the thing it answers.
Prayer campaigns run across the circle: a shared subject, prayed through together over a set stretch rather than once and forgotten.
A circle has a name, a member count and a conversation — not a feed, and not an audience.

No. Everything else in the app works on its own. Circles are there for the people who want somebody praying alongside them.
Yes. You can create one and invite people to it, or join a circle somebody else has invited you to.
No. A circle is a conversation among its members, with replies and reactions. There is no follower count and nothing to perform for.