This is your one-stop shop for quests. Each village has a girl who will give you your list of quests, allowing you to carry out your duty as a hunter. They are usually standing somewhere near either the village's quest gate or the kitchen.
If you're stuck on what key quest to do next, they'll sometimes drop useful tidbits of information on who needs what done (but it's not like you need that with this guide by your side, right?).