What is firefight in halo reach?

it is a game mode that puts you against wave after wave of aliens and specific skulls. there are 5 rounds and 5 waves. in each round the waves will get tougher and tougher(and so are the skulls). The skulls are settings to your game. they are disadvantages. (ex. the skull mythic doubles the enemy health). if you plan on playing firefight and you have xbox live play with friends or go on matchmaking. i wish you luck.