Olduvai Gorge is a steep ravine in the Great Rift Valley that stretches through central east Africa. The ravine was formed millions of years ago by an upwelling mantle plume separating tectonic plates; a process that continues.
That plume caused geographic changes on the surface that altered the biome over the course of millions of years. Those changes drove evolution at a time when hominids were emerging.
Olduvai is a misspelling of Oldupai. Since 2005, Oldupai has been the official name that nobody uses except the locals, who named it in the first place. Anthropology is an inexact science.
Olduvai Gorge is the most famous paleoanthropological site on Earth, and one of the most important, owing to its continued popularity as a prehistoric place to live. Homo habilis resided there 1.9 MYA. Paranthropus boisei called it home 1.8 MYA, followed by Homo erectus (1.2 MYA), and, most recently, Homo sapiens (17 TYA).
Not surprisingly, Olduvai Gorge has been a treasure trove of primitive tools, starting with sharp-edged lithic flakes. Although not the first place such tools were found, it gave its name to the earliest known lithic industry: Oldowan culture (2.6–1.7 MYA).
Famous archeologists Louis and Mary Leakey struck pay dirt at Olduvai in the 1930s, at a time of widespread skepticism that Africa was where hominins evolved.