Google first introduced video chat from Gmail in 2008, and now it has made the feature even better by including Hangout feature of Google+ in the Gmail.
Unlike the earlier process, when video chat was based on peer-to-peer (single person to single person) technology, with this new feature you can reach people on your Google+ list. You can also chat with those who are accessing their Google account through Android or iOS based smartphone or tablet from your Gmail account itself. You can watch the official video of this feature to understand what this really means.
All Gmail users will benefit from this upgrade, but if you and the person you’re chatting with also use Google+, you’ll get even more from the Hangouts experience. You’ll be able to video chat with up to nine people at once, watch YouTube videos together, collaborate on Google documents and share your screen (take screenshot and send).
Plus, Hangouts has a bunch of fun effects that you can try out, like pirate hat or mustache.
This feature is already available in Gtalk Android application, but the recent step brings this functionality to a wider number of devices so that one needs not be bothered about which device his/her friend is on.