but i've read that you don't have to compile everything from scratch each time you make a small change .
and can you explain what do mean by : " All it can do is run things for you so you can get on with something else "
You don't have to compile everything from scratch every time. One cpp file is compiled into one object file. If the cpp file hasn't changed, you don't need to recompile it, so don't recompile it. This has nothing to do with scripts; this is how C++ programming works.
If you use an IDE and it's sensible, it will keep track of this for you and only recompile the things that need to be recompiled. This has nothing to do with scripts.
can you explain what do mean by : " All it can do is run things for you so you can get on with something else "
Imagine you are typing something into your computer; lots of instructions that do things. Now image that instead of typing that in, you have it already written out in a text file and you order the computer to interpret that text file as if you had just typed it in. That's a script. It can't do anything magical; all it does is what you told it to do. You don't have to sit there and type all the commands in yourself; you can get on with something else.