Multitasking on the fourth-generation Apple TV is simple: Double-click the home button on the Siri remote (it's the one that looks like a TV), and then swipe to the right. Now, may see a different layout if you haven't updated to tvOS 9.2 yet -- that multitasking layout put apps side by side similar to how iOS 8 used to. With the latest update, Apple TV now reflects iOS 9's multitasking stack of apps. You can learn more about updating your Apple TV here.
If an app isn't running right, maybe freezing up on you, you can force close apps on the Apple TV by double-pressing the home button to bring up the multitasking view. Swipe to the app you want to close using the trackpad on the Siri remote, then swipe up; just as you would on an iPhone or iPad.
Multitasking makes it incredibly simple and quick to jump between two apps or games without having to go back to the home screen, then scroll through the app grid or folders to find an app.
Editors' note: This post was originally published on November 1, 2015. It has since been updated to reflect changes to the Apple TV interface.