The primary button on your iOS device is the Home Button. This button has various uses depending on how many times you push it and how long you push it.
From the lock screen, the home button is used to activate the screen. This brings up “Slide to Unlock” where you can simply slide your finger to unlock the device.
If you have set a passcode (which I highly recommend as a way of protecting your device), then you will have to enter it before you can begin using your iOS device.
The Home Button has a couple of other features from the lock screen. If you double push the home button, music controls will appear and you can control volume as well as the most recently played song, audiobook, or podcast without even unlocking your device.
If you triple push the Home Button your device will go into Accessibility Mode. This is a feature for those with sight impediments and will audibly read selected buttons and sections of the screen. To deactivate Accessibility Mode, simply triple push the Home Button again.
The Home Button can also be held down for 2 seconds to activate Siri (your iOS Device’s digital personal assistant) on the new iPad (3rd Gen) and the iPhone 4S and iPhone 5. To exit Siri, push the Home Button again.