IMEI Full Form is International Mobile Station Equipment Identity. It is a unique 15 to 17-digit number, which identifies individual mobile devices or other devices. Usually, this number is found behind the device where the batter is placed. Some mobiles display on screen, on entering certain keys on the phone. Usually, typing *#06# on the keypad of the device, displays the IMEI number on the screen.
Most often, IMEI is used to identify UMTS, LTE, and GSM-3GPP phones and some of the satellite phones. This code is mainly used to block the network usage of lost phones. Other than identifying and blocking service, IMEI has nothing to do with the subscriber. Several countries have acknowledged that use of IMEI has reduced incidents of phone theft.