|Horizons Vault has written a preview of Horizons:|
Most of the quests I’ve seen in the Beta were fairly simplistic and repetitive, but I believe that the game devs have a lot more in store for the Retail version than they have shown so far. Generally quests are given by certain NPCs (your class trainer and specialty trainers offer certain skill increases in return for quest completion in addition to NPCs who’s only job it is to give you quests) and are standardized on “kill 10 XYZ creatures”. One quest I had was to kill 10 level 10 creatures (of any sort). This quest was very simple for me because at the time I was level 18, but it increased my mage’s fire casting ability by a few points, so I didn't complain. Quest rewards normally will be gold and/or experience.