Accelerometer – Measures movement and orientation of your device. When you are looking at a photo and you turn your Lumia from portrait to landscape, and the image follows this movement to fill up the screen, this is the sensor at work.
Magnetometer – As a traditional compass is used to determine the direction of the Earth’s magnetic north pole the smart phones use something more accurately referred to as a magnetometer. The magnetometer can determine the direction of magnetic north, but it can also determine rotation of the device relative to magnetic north. In addition, it is also capable of detecting magnetic fields around the device. This an essential tool for location services.
Gyroscope – Measures the angular rotation of the device on three different axes. It is most useful when used in conjunction with other sensors, such as the accelerometer, to provide more accurate results.
Proximity – Its function is to disable the touch screen when you put the phone near your face for phone calls, and then switch the touch screen on again, when you bring the phone away from your ear to end the call. Your phone has this to prevent accidental selections during a call.
Ambient Light– This can monitor the light levels in your environment and adjust your screen accordingly. In a dark room, you won’t need your display to be so bright for you to see it. By adjusting the screen display brightness you can save battery life considerably.
For a list of supported sensors on your phone, see the device specification at http://www.microsoft.com/mobile/support.