If you have been reading Gamereactor on a daily basis, you probably know that Microsoft has been talking about the possibility of saving space on your hard drive by only installing parts of games, like removing dubbing from languages you don't speak or perhaps just having the next Call of Duty as a multiplayer-only game by removing the single-player altogether.
Now Xbox's director of program management Jason Ronald has explained this feature in Larry "Major Nelson" Hryb's podcast (fast forward to 51 minutes and 30 seconds), and says it simply lets you uninstall the parts of games that you don't want. A clever way to make your one TB SSD go further.
Ronald does, however, point out that the games must support this feature, so we assume there might be titles where this simply is not possible.