I haven't actually used Google+ but from what has been described by the newsless reporters it is Google's attempt at a "social network" vaguely similar to Facebook, Twitter, and the like.

To participate, you have to be registered with them, and be logged in as a "member." It's possible that you only see the G+ when you're currently logged in with Google, and perhaps it doesn't appear when you're not logged in(???).

Using the Google search engine, or the Google toolbar doesn't make you a Google+ "member."

While you're logged in at Google+, Google can track nearly everything you do on the internet, although of course they "don't take any personal information." If you're not logged in you're treated like anyone else, and Google can of course track just about everything you do on the internet, although of course they "don't take any personal information." Whether you're logged in or not, all the information collected is, of course, anonymous, but when you're logged in it's your personal anonymous information, which makes some people feel "more loved."

Google+ has created a new system for registered participants to view what information has been collected on them, to "delete" some of what may have been collected, and to make some changes in what kinds of things are "collected," but you can only change the rules for what's collected while you're logged in." While you're loggout out, you're like any other "anonymous" wanderer and information that's collected is limited to "whatever they want" - anonymously of course.

In other words, the G+ button is pretty much like the TwitterTwatter "Like" button and all the other "*** loves me and I'm special" buttons for the other "social" blather exchanges.

Google probably has a slightly different explanation.

John