Okay, so imagine you have a tunnel made out of a special material that is really soft and can be blown up like a balloon. When you blow air into the tunnel, it gets bigger and bigger and you can go inside and crawl through it.
It's kind of like when you blow up a balloon and then let the air out- the balloon gets small again. When you let the air out of the inflatable tunnel, it goes back to being flat and easy to store.
Inflatable tunnels can be used for lots of things! Sometimes they are used for parties or events, so kids can crawl through them and have fun. Other times, athletes might use them during training to practice running or jumping through tunnels.
So basically, an inflatable tunnel is like a tunnel that you can blow up like a balloon, and it's really fun to play with!