Android device have sensor that measure motion, orientation, and various environmental condition. These sensor can help you to play game that might track readings shake, rotation, or swing. A weather application might use a device temperature or travel application like compass might use the geomagnetic field sensor and accelerometer. About sensors, you can read from developer android for more complex information explanation or code.
Smartphone device like android are generally equipped with various sensors with different function. to find out sensors are embedded in the your android smartphone, you can install an application called “Android Sensor Box” from Google Play, which helps you to test those sensor.
Gyroscope sensor can measure six directions at a time. You will be able to see the effects immediately by rotating your phone slightly. Now Gyroscope sensor is mostly used in 3D game development, and possibly indoor navigation in future.
Light sensor is applied to detect the light intensity of the environment, and then adjusts screen brightness and determines whether to turn off the keyboard light. Test the effect by putting your phone in dark place and retrieving it.
Orientation sensor is applied to detect direction status of the device, i.e. auto rotate screen when device is rotated horizontally. It can also be used as measure equipment like Spirit Level.
Proximity sensor measures the distance between two objects, usually the device screen and our hands/face etc. Test the effect by moving your hand forward and backward in front of the device in Android Sensor Box.
Temperature sensor provides information about your device temperature, thus you can take action when the temp is too low or high.
Accelerometer sensor is applied to detect device directions, i.e. auto rotate screen when the device is rotated vertically. It is also widely used in game development.
Sound detects the sound intensity around you and provides you detailed information about the intensity changes.
Magnetic Field is used in many areas like metal detection and compass, which bring us lot convenience in our life.
Pressure is used to detect environmental pressure, thus to forecast weather and temperature.
There are some images from the sensor box android application that I use to test my android smartphone Lenovo S560.