FSW is pretty much what the Army uses as part of training during Sapper Leader course for Combat Engineers (I went though that last year) and some of the infentry schools.
It's a squad based leadership development and reinforcement. You are put in control of two (sometimes three) four man fireteams that include your teamleader (TL a sergeat), AR Automatic Rifleman with a m240 Bravo or an M249 SAW machineguns, G Granadeer with an M203A1, and a R Rifleman with an M16A2(A3,A4 ect).
The person in leadership position (you) then manuvers the two squads towards accomplishing a set objective utilizing appropriate squad movements such as Traveling, Traveling overwatch and Bouding overwatch. Each of the movement techniques has its pros and cons such as the amount of control over the fireteam, movement speed vs. security. You also renforce your movement with covering and suppressing fire when needed.
Basically its Ghost Recon + America's Army + Black Hawk Down. A very interesting game.A nice grab if you arent sick of the real "sand box" already
PS Cover, cover, cover... its there, use it and love it, it'll save your ***.