trying to learn f-strings - puzzled by format() protocol

[Skaperen]

in the documentation i see it say "An empty string is passed when the format specifier is omitted." is "format specifier" the "format_spec" that follows ":" (as in the next paragraph)? i don't see any format_specs in DeaD_EyE's code. but his print does not show arguments so i can't tell if __format__ was really called with an empty string.

in the syntax chart, the 2nd to last line has "format_spec ::= (literal_char| NULL |replacement_field)*". what does the * mean? that it can be repeated 0 or more times as in regular expressions?

this is in the PDF language reference for 3.7.4 (though i am running 3.6.8).