Today, Google announced a new update to the Google+ app that will be rolling out later today that brings a host of new features. For starters, the posts have been redesigned to look a little cleaner, provide more content up front, and are easier to interact with. For example, you can now swipe between photos in an album, and tapping content should take you directly to where you want to go. The current Google+ app has a problem with requiring the user to jump through several hoops to get to the meat of a post, so hopefully this makes things easier.
One of the biggest problems with Google+ has been its inability to create a group wherein all peers are equal. You can create a hashtag that everyone can post to but you can't control the membership of, or a Page that a few moderators can share to, but it's difficult to add users to (for non-public posts, Pages can only add users to circles once they add the Page first). Communities finally fixes this problem by creating public or private groups that anyone within can share to.
The Communities feature includes everything you would expect from a separate group: you can submit public posts that everyone can see, or just private posts that only members can access.