Surnames and Maiden Names

Hi

I have 2 Visbek Church Book records in question:
For the marriage of my ancestors it gives:

Johan Alerd Ahlers genannt Tonnies and Maria Gertrud Tonnies. What does this mean regarding last names? Was Johan Alerd born Johan Alerd Tonnies? Was he born Johan Alerd Ahlers, but took his wife's surname after marriage? Their decendent is a Tonnies.

I also have the case where it says:
Johann Heinrich Suing g____ Dietmann and Maria Elizabeth Suing, where their decendent was a Suing. Is this the same?

Thanks
Annette