Okay kiddo, so a hopper balloon is a type of balloon that can carry people or things up into the sky. It's kind of like a really big kite, but instead of being held down by strings, it's filled with something called "hot air" which makes it float up in the air all by itself!
Now, the hopper part of the balloon is the basket that dangles down from the balloon. This is where people or cargo can sit and be carried up into the sky. It's kind of like a magic carpet, but instead of flying through the air on a carpet, you get to fly in a basket hanging below a balloon!
The really cool thing about a hopper balloon is that you can control how high it goes by either adding more hot air, or by letting some hot air out. So if you want to go higher, you just add more hot air, and if you want to come down, you just let some hot air out.
Imagine being in a giant basket and slowly floating up into the sky, feeling the wind in your hair and looking down at all the tiny buildings and trees. That's the kind of adventure a hopper balloon can take you on!