OOOOOOOOOK esa i will answer that but first
this is master chief at midnight
heres some facts
By June 20, 2006, more than 500 million games of Halo 2 had been played and more than 710 million hours have been spent playing it on Xbox Live by May 9th, 2007, this number had risen to five billion, with more than five million unique players on Xbox Live.
nvm mind that heres a short summery of halo 1 and if u want to read the whole story then ill give links
The "Halo" in the title refers to an enormous artificial space habitat similar to a Culture Orbital discovered by the warship Pillar of Autumn, which the central character, Master Chief Petty Officer John-117, is aboard. With the help of his fellow marines and the ship's artificial intelligence, Cortana, the Master Chief discovers some of the secrets of Halo while fighting off members of The Covenant, archenemies of humanity who, presumably, wish to find Halo's secrets for themselves.
also the link for halo 1