IMEI Number is stands for International Mobile Equipment Identity. In other words we can say that it is the unique and secret mobile phones identity number.
Every GSM, CDMA, WCDMA, and iDEN Mobile Phone as well as some Satellite Phones have their IMEI Number or Code.
IMEI Number easily found printed inside the battery of the cell phone. It can also be displayed on the screen of the phone by typing *#06# into the keypad on most of phones like Nokia, Sony Ericsson etc.
The IMEI number is used by the GSM network to identify valid devices. It is used for stop a stolen phone or to recover or find stolen mobile phones by accessing the network.
For example, if a mobile phone is stolen, the owner can call his or her network provider and instruct them to “ban” or “blocked” the phone using its IMEI number. This renders the phone useless, whether or not the phone’s SIM is changed.