Inscription

Inscription is a crafting profession added in Wrath of the Lich King with which players can create glyphs, scrolls, cards and more! Scribes can use the learned skill Milling to break down herbs (gathered with Herbalism) into pigments used to create inks. These inks, both common and uncommon, can then be used to inscribe a parchment with a glyph or buff spell. Currently, scribes learn specific recipes through Northrend Inscription Research, Minor Inscription Research, and Book of Glyph Mastery from Northrend; this will be revamped in 4.2.

Glyphs are special items that can be used to enhance a specific spell or ability. There are three types of glyphs: Major Glyphs which affect key abilities, Prime Glyphs which shine in combat, and Minor Glyphs which yield small cosmetic improvements. At level 25 players unlock one of each type of glyph, at 50 two, and at 75 three, leading to 9 glyphs concurrently in use at maximum. In Cataclysm, players permanently learn a glyph upon use; if you want to switch glyphs though, you will need a Dust of Disappearance, created by Inscriptionists or purchased from vendors.

Scribes can also create scrolls that provide stat buffs to players such as Runescroll of Fortitude II, as well as random Darkmoon cards that can be combined to form powerful trinkets. Turning in these decks also grants the player reputation with the Darkmoon Faire, needed to complete Insane in the Membrane.

It's a moot point while leveling if you have access to BoA weapons, but scribes can create off-hand frills as well as relics. Some of these are ilvl 346 and very nice for starter gear options.

There's some fun vanity items: Rituals of the New Moon turns the user into a werewolf, and new to Cataclysm are Origami Beetle, Origami Rock, and Origami Slime.

Creating glyphs in a guild counts towards the achievement The Pen is Mightier. Inscriptionists can store materials in Pack of Endless Pockets, created by Leatherworkers.
Profession-specific Perk
Scribes can create and use powerful Master's Inscription shoulder enchants for Wrath and Felfire Inscription, Inscription of the Earth Prince, Lionsmane Inscription, and Swiftsteel Inscription in Cataclysm, which provide buffs far more powerful than those available from faction reputation vendors.

In addition, scribes have access to a daily quest: Forged Documents.