I believe its Google answer to Facebook its currently invite only at the moment and is still in devlopment before its opened to everyone I believe.
I like google products and own an android phone but I really cant see the point in this, social networking is obviouly big business but facebook works and most people have it trying to split the popularity between two sites just wont work as the would point of it is the ability to network and that means everyone needs to use the same thing. Just leave it alone google.
Just my opinion of course some people might love it I hated social networks at first because there were so many myspace hi5 bebo etc etc and I got soo bored of all the different people asking you to join but i grew to love facebook it because its got everything/one all in one place cant see it being displaced anytime soon unless its bought out or linked to google+