Before hominins intentionally chipped stone to make tools, they likely used sharp rocks already shaped by natural forces.

Two of the stone tools analyzed were made using the Levallois knapping technique of the Levant Stone Age, in which a flint stone core is essentially flaked away to make a point that can cut and hack.

Axes made from polished flint and stone were important throughout the Neolithic (Late Stone Age) and Early Bronze Age. Fine-grained stone was quarried from hillsides in Cumbria, Wales, Cornwall ...

so Stone Age people needed sharp, strong tools to cut trees down and to hunt the animals for food. And this is where a stone called flint came in. There's a real skill to making tools out of flint.