Marco's are skill I'll give you a few examples I use on my hunter over on wow
One macro is for my boar, and it intercepts on my focus target without me having to target anything I can set a focus and then i can intervene is need be
Another one is also really simple and saves me time, everytime i fire serpent sting i also apply hunters mark, this way if its an add fight I don't have to manually apply HM.
there are just to examples that good players would have looked into, and there are many more I use on a regular basis.