Regular expressions, or regex for short, are certain characters used as search functions. They are powerful, confusing tools. Justin Meredith wrote a guide on how to get started.

In case you don’t know, a piece of text within another piece of text is called a “string” in programming. For instance, the word ‘green’ is a string of characters from the text “I wore green pants today.”

So put another way, regex is a way to locate a string of text in a larger body of text. And because regex is written in code, you can use it to perform some pretty complex operations.