Okay kiddo, so have you ever seen those animations where a ball seems to bounce from one place to another in a smooth and continuous way? That's called beta movement.
Now, the trick to understanding beta movement is to realize that the ball isn't actually moving continuously from one spot to another. Instead, what's happening is that your brain is seeing a series of images of the ball in slightly different positions, and it's filling in the gaps between those images with the idea of smooth and continuous motion.
It's kind of like looking at a flip book, where each page has a slightly different drawing and when you flip through them quickly, it looks like the character is moving. That's what's happening in your brain with beta movement.
Scientists have studied this phenomenon and they think it happens because our brains are wired to see motion as continuous and smooth, even when the actual images we're seeing are jerky or disjointed. Isn't that cool?