WaterWheels have been used to power mills, saws, sifting flour, and for hammering stuff. The Egyptians used it for transporting water from river to land. When the Nile river was full, without the water wheel, they would have to move it by hand, but with the waterwheel, it was more accessible because it would move the water for them.
The water wheel didn't get used in Europe until after the roman empire fell apart. Because the Romans already had the number of slaves to do the work for them, and they didn't want to pay the money for an invention they weren't sure was going to work. So they stuck to slaves. But the reason it came back after the roman empire fell apart is that everybody had to help themselves. And the churches knew how to read and understand the Egyptian manuscripts on the waterwheel, and they had the funds to build it, so they created the waterwheel. They used it for hammering, milling flour, and many other tasks. Here are some videos on waterwheels: