Multiplayer is definitely worth trying out when you have the time.
A quick rundown of battle types in multi:
Deathmatch: All against all, if you die you respawn. The game ends when a certain number of kill has happened, and you get to see the guy with the highest number of kills.
Team Deathmatch: Two teams, aiming to get to a number of kills first, normally 300. The first to get there wins. If you die you respawn.
Battle: Two teams again, this time it's a series of round and you try and win the most rounds. If you die, you do not respawn until next round, the winner is whoever clobbers all their opponents first.
Siege: Same as battle, except there is a castle to capture, and the battle can be won by standing in an area to capture the castle.
These are a few, I'll list more later.