Circles are coming
A circle is a group you can post into. Built around a tag, or a few of them, or whatever else the people in it have in common.
Why create a circle?
Tags tell you who else is out there. A circle gives those people somewhere to actually talk. One place, everyone in it, everything posted to it.
Who can create a circle?
Anyone. You set one up, say what it is for and run it. Anyone who wants in can join.
What can I post?
Whatever you would say to the group. A question, something you have just worked out, a video, a screenshot. It goes to everyone in the circle and stays there.
How many circles can I join?
However many fit. Most people belong to more than one, so they overlap on purpose.