Hangouts with extras was an hangout incubator where google+ team tried and launched several hangout features before making it a part of the core hangout product.
Google+ hangouts with extras is freaking awesome! Added features Screen sharing, Sketchpad, Shared notes & Google docs!
One of the hottest and most used feature in Google+ social network is Google+ hangouts. To spice up further, google+ team is introducing quite a lot of features that are only found in paid commercial tools, absolutely free for Google+ users.