There are several classes of troops on Battlefront II. The basic infantry (Stormtroopers for the Empire, Clone troopers for the Republic, B-2 Super Battle Droids for the CIS, and Rebel troopers for the Rebellion) is for all four of the factions, along with the engineer class, the heavy weapons class, and the sniper class.
Each faction has two officers, which differ between factions. The Imperials have the Imperial Officer and the Dark Trooper. The Rebellion has the Bothan Spy and the Wookiee smuggler. The Galactic Republic has the Jet trooper and the Clone Commander. The CIS has the IG-100 MagnaGuard and the Droideka/Destroyer droid.