Single-element parethesized expressions/tuples vs common use of parentheses

Question

Sorry if this is trivial - I am so new to swift, actually I have only looked at the language guide+reference for a few minutes.

As far as I understand a parenthesize

Answer 1

+, * etc are infix operators, and they have a semantic meaning that's different from the comma ,, so the compiler treats it in a different way.