Okay kiddo, have you ever seen those cool stickers you can put on your bedroom walls? That's called a wall decal! It's basically a sticker that you can put on your wall and it looks like it's a picture or a design that's actually part of the wall.
Here's how it works: You pick out a design that you like, like maybe your favorite superhero or a beautiful flower. The design is printed onto a special type of vinyl that's sticky on one side. When you get it, you peel off the backing paper and then carefully stick it onto your wall.
The great thing about wall decals is that they don't damage your wall like painting or wallpaper would. So if you decide you don't like the design anymore, or you want to move it to a different spot in your room, you can just peel it off and it won't leave any marks behind.
So, that's a wall decal, it's basically a sticker for your wall that you can use to decorate your room and make it look super cool!