Okay, so imagine you are riding a horse and you want to go really fast and jump over things like fences. The way you sit on the horse and the clothes you wear are called "hunt seat."
When you ride a horse in hunt seat, you sit up straight with your shoulders back and your feet in stirrups. You wear special clothes like a riding helmet, tall boots, and pants that are snug so they don't get caught on anything.
Hunt seat is the style of riding you see in horse shows where the rider and horse jump over obstacles and are judged on how they look and how well they perform. It's a lot of hard work because you have to practice a lot to get good at it, but it's also really fun and exciting!