Ok kiddo, so you know how your toy cars can crash into each other and make a big mess? Well, the same thing can happen inside a computer!
See, a computer has a special part called a hard drive which stores all of the important information, like pictures, videos, and games. But if the hard drive's tiny little "arms" that read and write the information get too close to the spinning disk, they can crash into it - like two toy cars crashing!
This is called a "head crash" and it's very bad because it can damage the hard drive and make all of your important stuff disappear! That's why it's super important to be careful with your computer and not shake it too much or drop it, because that can cause a head crash too.