Text Patterns and Matches
A regular expression, or regex for short, is a pattern describing a certain amount of text. On this website, regular expressions are highlighted in red as regex.
This first example is actually a perfectly valid regex. It is the most basic pattern, simply matching the literal textregex. Matches are highlighted in blue on this site.
We use the term "string" to indicate the text that the regular expression is applied to. Strings are highlighted ingreen.