eli5: how do gears work on a pedal bike and how do you use them to make cycling easier?

Question

I’ve tried reading explanatory articles and I just don’t understand. Feels like a dumb question but they all say things like “shift down gear” and I don’t know what that actually physically means doing to the gears. Or, the articles assume I have a bike to look at and test it out on, which I don’t.

In: 2

Answer 1

If it’s shorter it takes less energy to make a full turn but also the same force from you reaches the ground without being wasted as much

The shorter the more force going to the ground