*** Posted by Rapier ***
[Please tell me what is the role of the second pilot in two seat F16?]
The second seat is for taking people like me and you for joy rides. No, only joking. Seriously though 2 seated aircraft are used for a number of reasons. They could be used to give wanabee pilots a chance to take the controls with an instructor on board to get a feel for the F16 and learning the BFM.
As you may know in the F-15 and F-14 for example the rear seated pilot is known as the RIO and is able to take control of the weapons systems and bomb attack role while leaving the pilot to fly the plane. Even when in a dogfight the RIO can keep an eye on the bogey/s while he locks several of them up onto the weapons systems leaving the pilot to perform and fly the plane the way he has been taught. It's all to do with team work and sharing the work load.