Some components of the game are characters such as the Master Chief, Captain Keyes, Sergeant Johnson. Cortana, the Arbiter, Gravemind, and the Prophet of Truth. Some other components of the games are the alien and human vehicles, the human and alien weapons and alein enemies. there are two different sets of alien enemies. Half are the Covenant species which consists of Grunts, Prophets, Jackals, Drones, Brutes, Elites, and Hunters. The other alien race are the flood which can take over an allies or enemies body and turn them into one of the Flood.
The game has 10 different levels that each take place in a different area. in some levels the layout is the same, but the area is more rugged with much more enemies. the game also has four different levels of difficulty. the first is easy, then normal, then heroic, and lastly legendary.
The rules of the games are to get through every level. you can die an unlimited amount of times but you can start back at the last save point.