Tags and keywords
For reference, the associated policy note (you don't need to visit it yet):
String pseudo "type" indicators are often used in combination with the option '$opt$return' in help registration functions of the HelpF` and HelpO` packages for indicating possible return type or formats of functions or methods in human-friendly form. Their use is entirely optional, and they play no role at all in the code.
They may be also used in combination with 'type$' indicators for Webel '$arg$' and '$opt$' help holders as we'll see in later slides and in a later trail section:
Notes
[CONVENTION, NAMING, PATTERN, POLICY]{STRONG} Webel: Mathematica: CONVENTION: A 'type$' indicator for an '$opt$' or '$arg$' is for documentation only. It may use a "pattern helper", a human-friendly String, or a SysML-similar short-hand type representation. It need not correspond to a valid Pattern.