All magical weapons are intelligent. (Maybe all magical armor, too).
Intelligent items have scores for INT, WIS and CHA. At certain times, a weapon may attempt to dominate its owner, or the owner may wish to dominate a strong-willed weapon. The dominator proposes a course of action that the potentially-dominated would otherwise not take. Weapons usually do this to fulfill some special purpose. For example, a sword meant to kill orcs may force the wielder to attack an orc even when its inconvenient.
The check for dominance is CHA versus WIS. Chance of success on d20 is 10 + target’s WIS – dominator’s CHA. Any calculated chance below 2 means automatic dominance. Any chance above 20 means no chance of dominance. A successful domination means the the target must accept the proposed course for a day before another check is made.
(Note how this varies from http://www.d20pfsrd.com/magic-items/intelligent-items/)