Titles are well...titles. They appear above your character's name in yellow text. Most title's are gotten through quests, but a few are from skill books and events. All titles have effects that improve your character's stats; to set a title press "T" in-game, and at the bottom there will be an option for changing your title.

Here is a list of the titles:

Name Effect Level obtainable How to Obtain
Indomitable Explorer +5% Defense 15 Quest: What We Need Is An Adventure
Behemoth Adventurer +10% Back attack damage 20 Quest: In and Out
Rope Dancer +50% Rope and Ladder Movement Speed 21 Quest: Where Is Lemy?
Wanderer +10% Movement Speed 25 Quest: Find Nana
Great Hero +15% HP & SP Recovery Rate while resting 31 Quest: Defeat the Fake Great Monkey
JumpJump +10% Jump Attack Damage 41 Quest: Fruits of Adventuring
Tough Explorer +7% Defense 50 Quest: Tough Life For You
Multiplayer +3% Max Physical and Magical damage, and +3% Movement Speed 60 Quest: Hidden Ring
Snow Lady +5% Stamina and Magic  ?? Skill Book?
Wind's Child +5% Strength and Defense  ?? Skill Book?
Night Owl +13% Movement Speed 80 Quest: King of the Ninja
The Tallest Tree Winner +150 HP; +70 SP 63 Quest: -To be edited-
Wilderness Adventurer +5% Max Physical Damage; -5% Evasion  ??  ??