Structure of IMEI and IMEISV

IMEI is called International Mobile station Equipment Identity.
As the name suggests it recognizes the manufacturer of the mobile equipment. It is a serial number which is allocated by equipment manufacturer, and is used to register to network operator, which stores it in EIR (Equipment Identity Register).

This is the serial which is used when your device gets stolen.
IMEI is of total 14 digits pus a check digit, while IMEISV is of 16 digits., this includes information on origin, model, and manufacturer of device.

Format of IMEI: AA-BBBBBB-CCCCCC-D
IMEISV: AA-BBBBBB-CCCCCC-EE

IMEI has following parts:

Type approval code(TAC): 6 decimal places (AA-BBBB), centrally assigned and tells about model
Final Assembly Code(FAC):2 decimal places (BB), tell about location of device's construction and is manufacturer specific.
Serial Number(SNR): 6 decimal places, assigned by manufacturer.
Spare/Checksum: 1 digit

IMEI = TAC+FAC+SNR+Checksum

In the new format of IMEI, FAC doesn't any more exist, now TAC is made 8 digits long and rest all is same.

IMEISV(IMEI Software version): contains 14 initial digits similar to IMEI but last 2 digits are called as Software Version Number (SVN)

To know your IMEA number on your handset, dial *#06#
Now based on this IMEI you can find out information about your device using below site:
IMEI Number Lookup

Example:
49015420: 
Issuer:BAPT

Brand: Nokia
Model: 3110
Manufacturer: Nokia Mobile
Devie type: Phone

A list of Manufacturers and thier TAC is vailable at below link:
List of TAC