Oldowan tools are crude stone tools formed by pounding (or knapping) flakes away from a pebble (or cobble) of flint, chert (chalcedony), jasper, obsidian, and even coarser-grained quartzite river pebbles to create a serrated edge. This edge would serve as a chopping blade, as a scraper, or a primitive knife. (The flakes could also find use as tools.)
Tools like these were used by early hominids such as Homo habilis and have been discovered at sites in Africa including Olduvai Gorge, Rift Valley in Tanzania (from where the name originates), East Turkana, Kenya, Swatkrans and Sterkfontein, South Africa, and Omo, Ethiopia.
It is also possible that other materials such as wood and bone were used by Homo habilis - such bone tools have been discovered at Olduvai Gorge and Sterkfontein.