Regular Expression (aka “Regex”) is used to search a particular text pattern. Using Regex in a computer program, a developer defines the way to search and perform an action on a particular string. You can use ASCII characters such as digits, letters, symbols, and punctuation to look for a string. You can also use Unicode characters for matching an international text. For example,  Regex can tell you all the text files in a program. It is highly efficient where one needs to perform activities like searching, processing, and validation of a text pattern.