Induction!

Did you ever do the experiment where if you coil a wire, and then hook it up to a battery, it becomes magnetic?

Well it works in reverse, too. If you move a magnet near a coil, it generates power! Specifically, its the motion of the magnet that makes power, so the magnets are mounted to the spinny spinny bit and the coils are in the base hooked up to the grid.

(this is an oversimplification)

In slightly more detail, motors work on the same principle, since they’re just magnets and coiled wires. Apply power to the leads to spin the motor, but also, you can spin the motor by hand like a crank to generate power at the leads.

This is also how wireless charging works. Power goes into a wired coil that makes a magnet that makes power in another wired coil inside your phone,