Three different ways to say 'how are you?'
Hi there! I've been taking the German course on Duolingo for a while now, alongside the Duolingo counterpart course on Memrise and the Memrise-created German course. On the latter course, I was taught two new ways to say 'how are you?': "was geht ab" and "wie geht es dir?" My question is: what is the difference between those two and 'wie geht's?" Are they simply more formal, or are they the same thing?
Wie geht es dir? this is the informal way you greet people you know rather well, also you can greet your pets with it. Wie geht es Ihnen? Is for a formal greeting, of someone you just met/don't know very well, authority figures, etc. Was geht ab? Is more colloquial German. Wie geht's, the 's replaces es dir, In the Wie geht es dir (form).