Fire support is... a lot of things...
Among them is probably... Through means of utilising your weapon fire to the fullest, fighting in a way that complements/benefits your allies by intelligently overloading enemy priorities, constricting enemy freedom to manuever, forcing gaps in enemy formation or durability for allies to exploit (either go for allies and get blasted by me, or go for me and get blasted by allies, choose one), if not killing them straight. Killing should be your goal more of when it would benefit your allies more.
Thr difference between that and the frontline/assault/trooper would probably be a tanking component or active effort in reducing enemy attention to the frontline.
It also reduces crowding around with the rest of your allies, hence freeing up manuevering space, especially in confined spaces.
Basically the difference between effective fire support and just shooting is the tactical consideration.
My articulation seems off somehow, but I hope I got the point across.
Edited by Matthew Ace, 23 June 2015 - 06:51 AM.