Humans have senses (touch, hear, smell, and so on); a phone has digital "senses": touch, geolocation, orientation, and motion. A sensor is a device component that measures a physical quantity and converts it into a signal that is understandable to software. Modern mobile phones come with a variety of sensors that can support users when completing their daily tasks. By tapping into a device sensor, you can enhance the end user experience and develop sophisticated apps.
Sensors can be hardware-based or software-based. Hardware-based sensors are physical components built into a handset or tablet device. They derive their data by directly measuring specific environmental properties such as acceleration, geomagnetic field strength, or angular change. Software-based sensors are not physical devices, although they mimic hardware-based sensors.
Typical device sensors are the accelerometer, gyroscope, compass, barometer, orientation sensor, and so on.