Android can now limit how apps function in the background, thus improving a user's battery life and the device's interactive performance. (pocket-lint.com)
Because Modern apps function like mobile apps, there's no reason to close them when you're done with them. (howtogeek.com)
When you «Choose default apps» you can assign several primary app functions such as your default web browser, e-mail program, music player, and more. (howtogeek.com)