You know how to tell a lie.
Bluff is an opposed skill check against your opponent’s Sense Motive skill. If you use Bluff to fool someone, with a successful check you convince your opponent that what you are saying is true. Bluff checks are modified depending upon the believability of the lie. The following modifiers are applied to the roll of the creature attempting to tell the lie. Note that some lies are so improbable that it is impossible to convince anyone that they are true (subject to GM discretion).
You can also use Bluff to feint in combat, causing your opponent to be denied his Dexterity bonus to his AC against your next attack. The DC of this check is equal to 10 + your opponent’s base attack bonus + your opponent’s Wisdom modifier. If your opponent is trained in Sense Motive, the DC is instead equal to 10 + your opponent’s Sense Motive bonus, if higher. For more information on feinting, see Combat.
You can use Bluff to pass hidden messages to another character without others understanding your true meaning. The DC of this check is 15 for simple messages and 20 for complex messages. If you are successful, the target automatically understands you, assuming you are speaking in a language that it understands. If your check fails by 5 or more, you deliver the wrong message. Other creatures that hear the message can decipher the message by succeeding at an opposed Sense Motive check against your Bluff result.
If you fail to deceive someone, any further checks made to deceive them are made at a –10 penalty and may be impossible (GM discretion). You can attempt to feint against someone again if you fail. Secret messages can be relayed again if the first attempt fails.