I first became interested in levers when I started doing renovations on an old house. I am not a particularly strong person physically, and I had trouble doing certain tasks like removing rusty nails from door frames and such.
The magic of levers is that they can convert a small amount of energy into a big force. Just by placing the head of a crowbar in a different position, my puny little force on the other end of the crowbar could remove nails. Magic!
Where the crowbar meets the piece of wood is called the fulcrum, represented by the triangle in the image. When the distance from the fulcrum to the nail is reduced, the amount of force on the nail is increased even if I’m not pushing any harder on the other end of the crowbar. And thusly, my not-so-muscular self was able to remove old, rusted nails.
You can learn more about levers in Chapter 3 of Physics for Animators.