Yep, what TB666 said. This is like Risk, 3-D chess, and Civilization 3 all rolled into one. The campaign map sort of resembles the game of Risk. The 3-D chess part comes in on the battlefield. I say that because it is quite difficult to win (but it is possible) when your enemy captures or kills your king. So you want to protect your king with your infantry (pawns) and cavalry (knights). You do all of this while trying to kill or capture the enemy king, although this is not needed in order to win the battle.
If you like Age of Empires, Cossacks, and Warcraft 3, you are going to drool over Rome: Total War. No it's not anything like those other games, but they are in the same genre.
TB666: Yeah, I know Cavalry will be able to take out charioteers, but I am not sure as to how effective they can take the chariots out. You're going to probably have to sacrifice a unit of cavalry just to destroy a small band of chariots.