This class represents a regular expression, with which you can perform matches against various strings and retrieve submatches (those parts of the subject string that match parenthesized expressions.) For example, given the regular expression

brown (\S+)

and subject string

The quick brown fox slyly jumped over the lazy dog

your Regexp object's Text property would be

brown fox

and its Submatches[1].Text property would be

fox

This is just a simple example of what regular expressions can do for you when parsing textual input; they are a very powerful tool. For example, the following regular expression will extract valid email addresses for you:

(?i)\b[a-z0-9._%\-]+@[a-z0-9._%\-]+\.[A-Z]{2,4}\b

See also PCRE Pattern Syntax.