Okay kiddo, you know how when you watch a movie or a show, sometimes the colors look really bright and sometimes they look kind of dull? That's because the way we see colors on screens can sometimes be different than the way they look in real life.
But scientists and engineers have been working on a way to make the colors on screens look more like they do in real life. They call it "rec. 2100".
Basically, rec. 2100 is a set of rules that tell people how to make screens show colors in a more accurate way. It's like a recipe for making colors look just right.
Now, this rec. 2100 thing doesn't just make the colors look better, it can also help people who are watching shows or movies on different devices, like on a phone, computer, or TV, all see the same colors. That's because all of those devices will use the same recipe for making the colors look just right.
So, in short, rec. 2100 helps make colors on screens look more like they do in real life, and helps us all see the same colors no matter what device we're using. Cool, huh?