Help - Glossary - C - Characters
The class Character is for dealing with characters, which are letters, digits, and some special symbols like tab, and cr. The way to indicate that what follows is a character is to precede it with a dollar-sign:
$a class. "Cmd-p gives its class"
$A. "Cmd-p prints it"
The above are two characters.
$ . "The character called space"
$$. "The character called dollar-sign"
Glossary - C