Short answers, pulled from the story.
The Oldowan, also called Mode I, was a widespread stone tool industry of the early Lower Paleolithic, spanning the late Pliocene and the first half of the Early Pleistocene. Tools were made by chipping one or a few flakes off a stone using another stone, and were used across much of Africa.
The oldest known Oldowan tools were found at Nyayanga on the Homa Peninsula in Kenya, dated to around 2.9 million years ago. They were discovered near Paranthropus teeth and two butchered hippo skeletons.
It is not known for certain which hominin species made Oldowan tools. Their emergence is often linked to Australopithecus garhi, and their flourishing to early Homo species such as Homo habilis and Homo ergaster. There is also evidence that some species of Paranthropus used stone tools.
The Oldowan takes its name from Olduvai Gorge in Tanzania, where the archaeologist Louis Leakey discovered the first Oldowan stone tools in the 1930s.
The Oldowan was followed by the more sophisticated Acheulean industry, which began appearing around 1.7 million years ago while Oldowan tools continued to be produced alongside it. Other tool-making traditions appear to have replaced Oldowan technologies by about 0.25 million years ago.
Oldowan tools were made mostly from quartz, quartzite, basalt and obsidian, with flint and chert coming into use later. River cobbles were the main source of raw material, supplying both hammerstones and striking platforms.