The regex search function is a tool that allows you to search for patterns in text using regular expressions. A regular expression is a sequence of characters that defines a search pattern, which can be used to match or replace strings, or to perform some other manipulation of text. The regex search function can be used to find matches for a specific pattern in a string, or to extract information from a string based on the pattern.

For example, you can use a regular expression to search for all occurrences of a specific word in a string, or to extract all email addresses from a block of text. Many programming languages, such as Python and JavaScript, have built-in functions for working with regular expressions, and there are also many third-party libraries available for advanced regex functionality.