The Loremaster

The Loremaster is a meta quest achievement earned for completed a high number of quests in each continent of the game. Daily quests do not count toward this achievement; some other repeatable quests only count the first time they're completed.

Title
The title obtained from this achievement precedes the character's name in the following format:
 * Loremaster 

Letters from the leaders
The Loremaster's Colors — the other reward from this achievement — comes in the mail attached to a letter. Alliance characters receive a letter from Tyrande Whisperwind.

Horde characters receive the following letter from Baine Bloodhoof. Prior to the Cataclysm, this letter was sent by Cairne instead, and still retains his signature.

Cataclysm changes
With the changes brought by the Shattering, the Loremaster meta-achievement also changed. New achievement – Loremaster of Cataclysm was added, and both Loremaster of Eastern Kingdoms and Loremaster of Kalimdor changed to meta-achievements similar to those from Outland and Northrend, and contain specific zone loremaster achievements.

Those who achieved Loremaster prior to Cataclysm retain the achievement and all that comes with it without having to fulfill the new requirements. Also, if the quests in a particular zone were not reset with the expansion (especially in Outland and Northrend) then the character automatically gained the achievement for that zone if he/she had already fulfilled the requirements for it. Otherwise, the new zone achievements are available to pre-Cataclysm Loremasters to do if they wish.

Loremaster in Mists of Pandaria
Rather than a certain number of quests, the zones on Pandaria require that the player completes the story line for the entire zone. Each piece of the story chains into the next, so it is easier to keep track of one's progress through the zone and does not require players to go looking for that one quest that's in an isolated area and easily overlooked. Completing the achievements for all the zones yields Loremaster of Pandaria.

As with Cataclysm, players who received the Loremaster achievement prior to this expansion keep the title and rewards that go with it, though they can still get the zone- and continent-wide achievements for completing each zone's story line.

Loremaster in Warlords of Draenor
Much like Loremaster of Pandaria, the achievements for Loremaster of Draenor requires completing all the storylines in each zone, rather than completing a certain number of quests. Loremaster of Draenor is also one of the requirements for Draenor Pathfinder.