• is denoted by [listOfCharacters]
• matches any single character from the list of characters

Shorthand is available for ranges of characters   [first-last]

E.g. [a-e] [a-z] [0-9] [a-zA-Z] [A-Za-z] [a-zA-Z0-9] [ -~]
(the last matches any printable character)

The matching can be inverted   [^listOfCharacters]

E.g. [^a-e] matches any character except one of the first five letters

Punctuation characters (except for ^\-[]) lose their special meaning inside bracket expressions.