The basic use is navigation (the N is GNSS). That capability can be used for both civilian and military purposes. Chances are that even though it will be used by the Indian military it will be used far more often for civilian purposes.
Yet on the use cases for this, I don't think India would have ponied up the money for this if it wasn't for the military use. With GPS, Galileo, Beidou and Glonass, the civilian navigation problem is pretty much solved. Are you aware of a use case it is solving that the others aren't?
