Cscope is like a treasure map. When you want to find something specific in a really big book or collection of books (called source code), you use cscope to help you find it.
Imagine you have a huge toy box filled with tons of toys. You want to find your favorite toy car. Without cscope, you would have to dig through the whole box, one toy at a time, until you finally found your car. But with cscope, you can type in "toy car" and it will show you exactly where the car is in the box, so you can quickly and easily find it.
In the same way, when you are programming and need to find where a certain function or variable is used in a really big program, you can use cscope to help you find it. Cscope helps save you a lot of time and makes it much easier to navigate through large, complex source code.