Quest

What are they?
Quests are in-game challenges where a player or group of players solve challenging riddles or puzzles for a special reward; some quests in fact involve challenging Monsters a lot of time. People who reveal quests in public channels or elsewhere to ruin the fun of other people trying to figure out a quest on their own are called quest spoilers. This website is popular because it engages in quest spoiling.

Purpose
They have many purposes, getting money, getting rare items or just have fun with friends.

How can I start one?
Talk with NPCs, ask them about missions or just have a chat with them and you may find something interesting. Other ways include spoiling the quest by searching in sites or asking players.