Regular expressions or regex or regexp are basically strings of character that define a search pattern, they can be used for performing ???Search??? or ???Search & Replace??? operations as well as can be used to validate a condition like password policy etc.
Regex is a very powerful tool that is available at our disposal & best thing about using regex is that they can be used in almost every computer language. So if you are Bash Scripting or creating a Python program, we can use regex or we can also write a single line search query.