In computer programming there is this thing called regular expressions (or short RegEx). They are basically simplified patterns in a special format to find (and replace) text. They are very powerful, but also at first can be hard to understand. I struggled with them for years until I found RegExr. It allows you to live tests regular expressions and has a handy, really helpful cheatsheet next to them in the sidebar. Now I understand them much better and I'm actually happy, if I can use them.