Pan and Scan is like when you are watching a movie or TV show that is too big for your screen. You know how sometimes you can't see all the cool things happening on the sides of the screen because it doesn't fit? Well, Pan and Scan helps you by just showing you the most important part of the screen, like the people talking or the action happening in the middle.
So imagine you're watching a movie about a lion in the jungle. In the original big screen version, you might see the lion in the center of the screen with trees and other animals around him. But when it's shown on a smaller TV screen, the whole picture doesn't fit. So instead of seeing the trees and other animals, Pan and Scan will just show you the lion.
That way, even though you can't see everything the way it was originally meant to be seen, you can still enjoy the movie and understand the story. It's like taking a big picture and showing you just a part of it that's important.