An autoclave is like a magical oven that can kill tiny bad germs that you can't see with your eyes. It looks like a big metal box that can hold things like tools or medical equipment, even toys or clothes.
When you put something inside the autoclave, you close the door and turn on the heat. The temperature can get very, very hot, like when your mom bakes cookies in the oven. But instead of yummy cookies, the heat is used to kill all the germs that might be on the things you put inside.
It's like giving everything a really, really hot bath to make sure it's clean and germ-free. When the magic oven is finished, everything inside is also very, very hot, so you have to wait for it to cool down before you can take it out.
So, the autoclave is a special machine that helps keep things clean and safe from germs.