I borrowed this game from my next door neighbors. It's very fun to play and helps you learn strategy and teamwork. It's rated "M" but if you turn off decals (blood) then it could should be rated T or even close to G.
There are two modes in the game: Campaign and Multiplayer.
In Campaign Mode, you are the Master Chief, a special project by the military code named Spartan. You are a specially enhanced power marine with a suit that strengthens and guards you. Your ship gets attacked by the Covenant, a group of aliens trying to destroy the human race. The battleship you are on, the Pillar of Autumn, crash lands on Halo, a giant ring planet created by the Covenant. The plot is amazing and rather suspenseful and will keep you on the edge of your seat until you finish it. It is interesting enough to play several times through without being bored.
Multiplayer is what many people solely buy the game for. You can do multiplayer with up to 12 other players either on teams or in free for all. You can do capture the flag, slayer, king of the hill, and many other fun modes. Since you can ride vehicles such as the warthog, in which there is a gunner as well as a driver and passenger, you need much teamwork to be able to win the game. There is a wide range of weapons, and this means you need a strategy. If you find a sniper rifle, you go find someone with a machine gun and shotgun and let them guard you while you snipe. You can organize your team to stay at the base, equip up, and all get into various vehicles and attack simultaneously to overwhelm the enemy forces. There are vehicles such as machine gun/rocket launcher equipped jeeps (warthogs) alien flying gunships (banshee), hovering attack bikes (ghosts), and tanks (scorpions) that add alot more to the game.
This is a great game that I could recommend to anyone. Get it!