What is IMEI / What did the 15 digits imei indicates

To check IMEI (International Mobile Equipment Identity) to any mobile phone or cell phone.
In the main screen type * # 06 #

The information you get from the IMEI (International Mobile Equipment Identity)
XXXXXX   XX   XXXXXX   X
TAC      FAC     SNR    SP

TAC = Type approval code of your Nokia
FAC = Final assembly code of your cell phone
SNR = Serial number of your Nokia phone
SP = Spare