At any given time while you are using your iOS device running iOS 7 or later, you can swipe up from the bottom of the screen to bring up Control Center. This tray gives you access to toggles including Wi-Fi and Rotation Lock, a screen brightness slider, music playback controls, AirDrop settings, and quick shortcuts to apps and, on iPhone, a handy flashlight. This works on the home screen, in apps, and even on the lock screen.
For additional quick tips and tricks for iPad (Mini), iPhone, and iPod Touch, click here: Quick Tips