Circles: Circles are the key concept that make Google+ different from its competitors. Every friend of yours is put into one specific circle. You can have a circle for family members, for friends, for your boss, and even one for people you don’t really like but still feel obligated to include. Anytime you post something on Google+, you have the option to share it with everyone, or with just specific circles.
Hangouts: Hangouts are Google+’s take on video chat. You start a hangout, inviting whichever circles you want, and what you end up with is a video chat with everyone who accepts your invite. You can talk on camera, or show a Youtube video to everyone in the hangout.
Sparks: Sparks show you news on a specific topic you’re interested in. If you find a cool story, you can share it with your circles, and spark up a conversation with them.
It may be hard to imagine any social network taking the place of Facebook. But it’s a good idea to remember that people used to feel the same way about Myspace and even Friendster before that.