Regex (Regular Expressions) are sequences of characters that define search patterns, used for string matching and manipulation. They provide a powerful and flexible method for searching, replacing, and parsing text based on specific patterns. Regular expressions are widely used in data scraping to extract relevant information from unstructured data sources, such as HTML documents. By using regex, developers can identify and extract data like email addresses, phone numbers, URLs, and other patterns from text. Mastery of regex is a valuable skill for anyone involved in data scraping and text processing.