Imagine you have a robot servant living inside your computer. You can tell this robot to move files, start programs, or check if the computer is healthy.
Bash is the language you use to talk to this robot.
Usually, you point and click with your mouse to do things. That is slow. With Bash, you type out your commands. It is much faster. When you put a lot of commands in a single text file and tell the computer to run them all at once, that is called a Script.