URI.char_reserved-question-mark
You're seeing just the function
char_reserved-question-mark, go back to URI module for more information.
Specs
Checks if character is a reserved one in a URI.
As specified in RFC 3986, section 2.2,
the following characters are reserved: :, /, ?, #, [, ], @, !, $, &, ', (, ), *, +, ,, ;, =
Examples
iex> URI.char_reserved?(?+)
true