Void union (List &La, List Lb) why are we passing list a's address as the argument and not the list itself/or pass all of them as addresses?

[Szymon]

Hi ! Hello, I would like to ask you a question that I can not answer, void union (list &la, list lb) why are we passing list a's address as the argument and not the list itself/or pass all of them as addresses? Please kindly answer me please.