Okay kiddo, have you ever played the game where you connect the dots on a piece of paper to make a picture? Belyi's theorem is like a really fancy version of that game, but instead of making pictures, we're looking at weird shapes called "curves".
Now, in math, we like to understand things by breaking them apart and seeing what simple parts they're made of. So, we want to break apart these curve things and see what dots they're made of. But, these curves can be really complicated, with lots of squiggles and loops and twists, so it's not easy to just look at them and figure out what the dots are.
That's where Belyi's theorem comes in! It tells us that every curve can be broken down into a bunch of simple pieces, like a puzzle, and each piece is made up of dots that are all connected in a certain way. And, the really cool thing is that we can describe these dots and how they're connected using some math called "group theory".
So, by using Belyi's theorem, we can take these complicated curves and understand them better by breaking them down into simple pieces and seeing how they're all connected. And that's why Belyi's theorem is really important in math!