it's a rts so you do build stuf, but it's more complicated than just making a bunch of buildings and alot of marines. there's many types of building to upgrade a home base, while you have many types of troops to make as well. and then you have to give orders to your troops to take points of intrest in a map or to crush the enemy.
i'm a big halo fan and know more about it's storyline than most others. but the game is a revolution in rts, but it can be too hard for some, and unapealing to others. if you play rts before you may not like how it feels but it's great for any halo fan. and it's the best rts made for any console. the only way to get a better rts exprience is to play one of the few good ones on pc