Regular expressions, often abbreviated as regex or regexp, are powerful tools used for pattern matching within text. They consist of a sequence of characters that define a search pattern, enabling users to identify, extract, or manipulate specific strings of text efficiently. Regular expressions are widely implemented across various programming languages, including Python, Java, and JavaScript, making them versatile for developers. Their applications range from simple tasks, like finding specific words, to complex operations, such as validating email formats or extracting data from large datasets. Understanding regex can significantly enhance text processing capabilities in programming and data analysis.