Proximity sensor explained
A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. The sensor detects the distance to surfaces (cheeks and ears), and it can pause whatever activity it is in the middle of (playing music or browsing the web, for example) so the user can take a phone call. When the phone is removed it automatically resumes its previous activity. It turns the screen off while you are making an call to disable accidental touch events.