The Xbox One is pinning its success on the fact that is much more than just a video game console. Microsoft is looking for the Xbox One to become the centerpiece for family entertainment, which is why they included features like multitasking, TV controls, and apps.
These app, which include Netflix, Internet Explorer, Game Feeds, and more, can be accessed while playing a game or can take up the full screen. Similar to Windows 8 and even the iPhone, these apps and games stay open and continue running in the background, which means you've got more processes going on than necessary, but here's how to close them.
In order to close down these background apps and games, you will need to hover over the app or game in the window on your home screen and hit the Menu button (the one with the three lines) on your controller. Now, go over and hit Quit and that's that.
You can also check out the Xbox One support page for more info.