Interesting mechanical fact:

This is a GIF I made to help explain to my son this interesting mechanical fact. ..in the GIF, the gear on top is called a worm gear. It's driving the big sprocket. That's the only way it will work. It's not possible for the sprocket to turn the worm gear.

It's interesting because that fact makes the arrangement of those gears very safe when control is an issue. Just stop turning the worm gear and everything stops and doesn't need any kind of brakes to keep it from continuing to move, like in an overhead winch or a gantry crane. ..also, the weight of the load won't add wear and tear on the motor that drives the worm gear when the load is just hanging.

If the sprocket was being driven by another sprocket or a mitered gear or something like that, it would require a brake of some sort to be applied to be able to achieve the same result the worm gear does for free, and does a better and safer job of it..