What is Google+?
According to Google, the idea is to make sharing on the web more like sharing in real life. Essentially, the user experience is similar to that of Facebook (a news feed based on status updates and shared content, recommended friends, etc.), but the idea here is to make it easier to share content with specific sets of people (called Circles) instead of just publishing content on your wall for everyone to see.
Google+ new components include Circles, Huddle, Hangouts, and Sparks.
Circles is just a way of setting up personalized social circles, whether they be centered around work or personal activities. Rather than share all updates with an audience of hundreds or thousands, the service aims to personalize sharing with smaller groups.
Huddle is a group chat for phones. Rather than individually sending SMS messages, Huddle can pool them together to make a group chat which is still private to outside viewers, unlike Twitter.
Hangouts also allow group chats with text or video for up to ten users. With Hangout, you can signal availability to some or all of your circles.
Sparks is a suggestion engine that finds interesting Web items based on your interests. You can pick from categories of interest and share items you find with others in your stream.