A concise and flexible notation for finding and replacing patterns of text. The notation comprises two basic character types: literal (normal) text characters, which indicate text that must exist in the target string, and metacharacters, which indicate the text that can vary in the target string. You can use regular expressions to quickly parse large amounts of text to find specific character patterns; extract, edit, replace, or delete text substrings; or to add the extracted strings to a collection in order to generate a report.