Hangouts are arguably the most popular feature of Google+, and Google has gone out of its way to promote various, prominent Hangouts. The company has also used the medium to have plenty of its own, connecting with users and/or providing in depth discussion amongst staff for the users' benefit.
Google introduced Hangouts with Extras in September. This was a set of tools to enhance the Hangouts experience, including things like: screensharing, Sketchpad and Google Docs support, and hangout naming. Google is now doing away with Hangouts with Extras, however, in favor of just making this stuff part of Google Hangouts themselves. In other words, they will no longer be extra. They'll just be part of the experience.
Google's Chee Chew said in a Google+ post, "Last year we launched hangouts with extras as a way to preview certain features (like screensharing and google docs). Since then we've graduated nearly all of these extras to hangouts proper, and yesterday's launch of hangout apps provides even more things to do together and opportunities for developers to expand the experience."
"Looking ahead, we think it's important to focus on the core hangouts experience -- both to reduce complexity, and to release new features more quickly," added Chew. "So as a result, we're going to phase out hangouts with extras over the next few weeks. There is, of course, one major extra not yet graduated -- the ability to name a hangout -- rest assured we'll bring it to hangouts proper before retiring extras completely."
Last month, Google announced that Google Docs are now a core port of Hangouts.
Since then, Google launched the Google Hangouts API opening the door for all kinds of real extras built on Google Hangouts.