The Uffington White Horse is a really big picture of a horse that has been carved into the side of a hill in England. It's been there for thousands of years! It's called a "white horse" because it's made of chalk, a white rock that is really good for carving.
The horse is so big that you can see it from far away, like a giant picture in the earth. In fact, it's so big that people used to think it might be a real horse that had been turned to stone by a magic spell!
But it's not real - it's just a picture. Nobody knows for sure why people made it so long ago, but some people think it might have been a way to honor horses or to show off to other people who lived nearby.
Now, lots of people go to visit the Uffington White Horse because it's such a cool thing to see. It's a really special part of England's history!