Okay, imagine you want to look at something really far away, like a star, but you need help because it's too small to see with just your eyes. A schmidt-cassegrain telescope is a special type of telescope that helps you see faraway things, like stars and planets, up close.
The telescope has a big, round mirror at the bottom that collects light from the faraway object you want to see. The mirror reflects the light up to a smaller mirror at the top of the telescope that bounces the light back down to a small hole in the middle of the big mirror.
The light then goes through a lens that magnifies it and makes the object you're looking at appear bigger and closer. You can even attach a camera to the back of the telescope to take pictures of what you're seeing.
Think of it like a really big, fancy magnifying glass that helps you see things in the sky that you couldn't normally see with just your eyes.