Unity is Ubuntu's new desktop environment.
Unity was originally concieved to provide a fresh desktop experience for Ubuntu users. It's designed to be easy to use, unique, innovative, and good looking.
Unity and its range of technologies brings simplicity, power, and integration to both users and application developers. Unity puts design and free software at the heart of delivering a powerful and attractive experience.Unity is now the default desktop experience in Ubuntu 11.04, so all users will get to experience this radical change from the traditional GNOME desktop from Ubuntu versions past.
Ubuntu still uses GNOME, however, and most of what you see on the screen is still GNOME technology. Unity is just a shell running on top of the regular desktop.
Because of this, if you don't like Unity, it's not that hard to change back to regular Ubuntu Classic Desktop from the login screen.
Founded in 2010 by Mark Shuttleworth and Canonical, The Unity Project has gone on to deliver a consistent user experience for desktop and netbook users alike.
Unity and its technologies such as application indicators, system indicators, and Notify OSD, have worked hard to solve common problems in the free software desktop whilst optimizing the experience for touch, consistency, and collaboration.