Threat

Threat is a special mechanic that is only used when you want enemies to attack your character. "Threat" basically means how dangerous the character, as perceived by the monsters/game mechanics. The more threat you have, the more enemies want to attack you. This allows others to attack them more easily and do more damage (via Sneak Attack), allows spell casters to cast Area of Effect spells more efficiently, keeps monsters away from vulnerable characters, etc.

Ways to improve your threat are using the Intimidate skill, which directly "threatens" the enemy, having a high Charisma to support it, feats (i.e. Skill Focus: Intimidate), enhancements (i.e. Improved Intimidate), and items (i.e. Intimidate +#)/buffs (i.e. Eagle's Splendor).