Okay kiddo, a curriculum is like a big plan for all the things you will learn when you go to school. Just like how you need a map to find your way to a new place, a curriculum helps your teachers figure out what they need to teach you and when they need to teach it.
There are different types of curriculums for different grade levels, subjects and types of schools. For example, in kindergarten, you’ll learn about colors, shapes, and numbers, and in middle school, you’ll study science, history, math, and English. While in High School, you'll have many specialized subjects such as biology, chemistry, physics, literature, and many more.
The curriculum is important since it helps everyone know what they need to learn, how to learn it, and when they should be ready to move on to the next thing. That way, at the end of the school year, you will have gained new knowledge and skills that help you be ready for the next level.
That's a curriculum in a nutshell, buddy.