Craft

Player's Handbook v.3.5 (PH)3.5

Key Ability: INT
Trained Only: false
Armor Check Penalty: false

You are trained in a craft, trade, or art, such as alchemy, armorsmithing, basketweaving, bookbinding, bowmaking, blacksmithing, calligraphy, carpentry, cobbling, gemcutting, leatherworking, locksmithing, painting, pottery, sculpting, shipmaking, stonemasonry, trapmaking, weaponsmithing, or weaving.

Like Knowledge, Perform, and Profession, Craft is actually a number of separate skills. For instance, you could have the skill Craft (carpentry). Your ranks in that skill don’t affect any Craft (pottery) or Craft (leatherworking) checks you might make. You could have several Craft skills, each with its own ranks, each purchased as a separate skill.

A Craft skill is specifically focused on creating something. If nothing is created by the endeavor, it probably falls under the heading of a Profession skill (page 80).