,and和and的問題

if there is a , before and...that means the sentense ( clause) after and is not important

like .. Q :who is this lady?
A : she is my step-mum, and Peter's mum.
in this sentense..,,i just wanna say the lady is my mum. the clause after and is not important...just tell something more...

but if A : she is my step-mum and Peter's mum.
that means i want to specific that she is peter's mum + not my real mum....

有時D人會將食物名，列如...with...寫成...and...，如果是多個兩樣咪要用多個and。

其實兩個都得。「.........,and.........」係舊時用,依家好多都用「...........and............」。