An oil well is a deep, narrow hole in the ground that's used for bringing oil to the surface. You'll find oil wells in parts of Texas and Oklahoma, but you probably won't be able to create one in your own backyard.
When a petroleum company finds an oil-rich area, they start drilling oil wells there, drawing oil from the ground, processing it, and selling it. Oil wells have been around since fourth century China, when workers bored holes using drills attached to long bamboo poles. In North America, the oldest oil wells were drilled by a heavy metal tool being dropped repeatedly in one spot, before the spinning type of tool known as a rotary drill was invented.