ELI5: Explain Like I'm 5

garbage in, garbage out

Garbage in, garbage out means that if you put bad or wrong information into something, you get bad or wrong information out. For example, if you try to do your math homework with wrong numbers or if you type wrong information into your computer, you will get the wrong answer or the wrong result. So in order to get good results, you need to make sure you put good information in.