I'll be honest, Halo's story confuses the hell out of me. Not the general outline, I get that, but the specifics and history of the universe are presented as a mess for someone who just plays the games and doesn't get knee-deep in the external fiction. If goes without saying, but you should expect spoilers in the below image.
Why am I here? Who's that guy? When did that happen and what the hell did that thing just say? That sort of thing.
m So I'm appreciating this simple guide, laid out in chronological form, to the overall backstory of the universe, provided by GameFront. Though even after reading it through a couple of times, boy, they could have trimmed some corners there, made it a little neater.
Click on the image for the full and immensely long version.
Halo Story Timeline [GameFront]