Gyro

Gyroscope - allows the device to rotate the screen from portrait to landscape when you turn your phone as well as use the device orientation as a controller for games

Proximity Sensor - this usually turns the screen off when you hold it up to your head while on a phone call so you don't accidentally "push" any buttons

Accelerometer - this detects changes in motion and is useful for apps that require a "shake" to perform an action.

I hope this helps and I have moved this to the Android Lounge for you where more folks will see it.