Google has come up with a myriad of ways to help you discover content on Google+, and today you can add one more to the list. "Topics" are streams of curated content like people, communities, and collections. They appear in a special Topic card, which some of you might have seen before.
The Topics card links to things Google estimates you have some interest in, and there are hundreds of Topics already available in English, Spanish, and Portuguese. Google+ is showing me Topics for computer security, watches, and photography. I suppose that's reasonably close. Click on any of them and you'll go to the Topics page with links to all the individual "components" so you can follow them.
Google has been testing Topics on a limited basis for at least a few weeks, but today's announcement makes it all official. It's quite possible you'll see Topics in your stream right now, but it should be live for everyone in a day or so.