A decompiler is like a magical tool that can turn a computer program, which is just a bunch of code that a computer can understand, back into something that people can understand. Imagine you have a really cool toy that you love to play with, but one day it breaks and you can't figure out how to fix it. A decompiler can help you take apart the toy and show you how it works. In the same way, a decompiler can take apart a computer program and show you how it is put together.
Sometimes people want to look at the code of a program, but they don't have access to the original code. That's where a decompiler comes in! It can take the program and try to figure out what the original code was.
However, just like when you take apart a toy, if you're not careful, using a decompiler can cause some parts of the program to break or stop working correctly. So it's important to use a decompiler carefully and only when you really need to.