If you see an NPC with a golden exclamation mark over their head, it means they have a Quest to give you; if it's a blue exclamation mark then it's a Daily Quest instead. Returning to the Quest Giver once you've completed whatever the task was will see you rewarded in at least Experience and, sometimes, gain you another Quest in a chain.
If you have already reached the maximum Level, when you hand in a Quest you will receive four times the Experience reward in Gold instead.
The Main QuestsEdit
The King of Haven has disappeared, and the Castle Steward wishes you to search for any clues as to his whereabouts. Which is, of course, where you, the hero, come in.
The Main Quests come in Sets every 5 Levels (as in new ones unlock at Level 10, Level 15, Level 20 etc), and if you haven't reached the next required Level you'll be given one of the Progress to Level ?? Quests; if you have, you'll never notice a break in the storyline.
As you enter new fields, you'll find Quest NPCs that have (usually) one-off tasks that are completed by whacking bushes and critters or picking up randomly spawning items in the area you're exploring.
These are as they sound, quests that respawn each day and can be done over and over once the requirements are done. These will usually appear after having completed a Side Quest or series of Side Quests, yet another reason to do your best to complete all of those as you find them.
While technically just another set of Side Quests, Rosa's gather Quests can only be gained one at a time, and only if you've completed and handed in the prior Quest in the chain.