Got the Google+ Communities icon now.  Glad they have this, and I have been waiting for them to create an equivalent of Facebook's Groups.  Facebook's Groups feature is a really neat feature, and Google+ Communities is going to work the same way.  My high school's improv comedy club had (still has) a Group.

It's different than circles (or any other visibility limitations you set on posts) because normal posts still go out to the people that follow you (have you in their circles), whereas a post on a Group page (and presumably a Community page) goes out to the followers of that Group, regardless of whether they follow you.

For the people who disregard every feature that helps people connect if it doesn't somehow tie into existing "IRL" social life, I would say that my high school's improv club Group is the perfect example of that.  We shared videos of other's doing improv, ourselves doing improv, the improv club leader would post reminders about deadlines and shows, etc.

One could even create a Group/Community for a group of friends, though I haven't personally.  Sure, a small group of friends is all mutually following each other and they can just limit post visibility (that's not as smooth on Facebook though), but a Group/Community works in this way:

-When you're at the page, if you post from that page, the visibility is automatically limited to that group.
-When you're at the page, you see what's being posted in that group as you scroll down:  you're not talking back and forth between walls and tagging and and awkwardly jumping around (though that has its uses too).
-A group creator can even have all posts be public in the group I think, but they're just not visible in the news feeds of friends you don't want to bother.

I'm going to take a guess that Facebook Groups is probably considerably overlooked by its users.

Hopefully "Communities" will not be overlooked, and certainly G+'s sidebar design (on the desktop) really helps, but the name does not help.  Think:  let's create a Group for our improv club or let's create a Community.  Uh, no, we just want some way for members to communicate; we're not creating a whole global movement around our improv club or anything.  

Because I feel like that's what "community" invokes.

ETA:  Google should have really just called it "Groups" even though that's Facebook's word.  Because it's also an English word, and it's kind of obvious.
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