[quote]The Forerunners are?[/quote] The Forerunners are a long gone species that were the primary civilization in the Milky Way Galaxy for 10,000,000 years. After encountering the Flood and treating them as a disease, rather than the true threat they posed, they were forced to activate Halo, which resulted in their disappearance. [quote]The precursors are?[/quote]A species that predate the universe itself and have taken on many various forms and shapes. After creating the Forerunners, they mysteriously vanished 10,000,000 years ago. I'm purposefully not sharing details that have already been elaborated on for your own sake.