Hi Gaurav,
There are several platform licenses , Restricted (R ) , Unrestricted (UR), Failover (FO), and Failover Active/Active (FO-A/A) , each providing different types features benefits. I am providing a link bellow to give you details of these,.
You have to make sure the vendor provides you with same UR specifications otherwise you will need to purchase UR license if you get something deferent. For example (UR ) provides more features than a Restricted( R ) firewall see link bellow and you can make the choice depending on your current firewall deployment , in most cases when buying PIX they come as UR but if you do not specify the vendor that you need UR they may send you a ( R ) Restricted firewall.
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_data_sheet09186a00800b0d85.html
HTH
Jorge
Jorge Rodriguez