ELI5: Explain Like I'm 5

Gear train

A gear train is like a line of gears that fit together. You can think of them like a row of interlocking gears that move together. They’re usually made of metal and are circular with teeth around the outside.

The teeth fit together to move the gears when they turn. When you turn one gear, the other gears will turn too. This is how they work together to move something. For example, you might use gears to turn the pedals on a bicycle or the wheels in a car.