What is the difference using ,(comma) vs using *(multiplication)?

What is the purpose of using --(double negative)

Why sumproduct does not work if I change from z6 to "Yes" ($G$7:$G$450=Z6) to ($G$7:$G$450="Yes")?



=SUMPRODUCT(--($C$7:$C$450=X7), --($B$7:$B$450<=AC3), --($B$7:$B$450>=Z3), --($G$7:$G$450=”Yes”), $M$7:$M$450)


=SUMPRODUCT(--($C$7:$C$450=X7), --($B$7:$B$450<=AC3), --($B$7:$B$450>=Z3), --($G$7:$G$450=Z6), $M$7:$M$450)

SUMPRODUCT((C7:C450=X7)*((--$B$7:$B$450<=AC3)*(--($B$7:$B$450>=Z3))*(G7:G450=Z6)*(M7:M450)))