Camera: Used for taking pictures.
Flash: Used for taking pictures in low-light situations.
Microphone: Allows you to use your voice to interact with your phone.
Power/Lock Button: Wakes the touchscreen or puts it to sleep when you press it. Turns the device completely off or on when you hold it down.
Speaker: Plays sounds on your device.
Volume Buttons: Increases or decreases the volume on your device.