WoW Question, Yes, one more

[Yarkanat]

I just rerolled a human priest (my main is 41 Tauren Shaman)
and I would like to know Should I go Discipline or Holy? If anyone has some gides or general info about them It is greatly appreciated. My first time as a priest so I only know Holy=Heal, Shadow=DPS, but what is Discipine? Is it a combination? Wouldn´t want to be shadow, since I kind of like healing

 

[Yarkanat]

Im just casual playing for fun with my mate with this alt so im not longing for lighning fast leveling, just something to do when I get bored of waiting for instances with my shaman Should I spend my first points to Discipline or Holy? Which one is better for early game?