Deceit is the ability to use language, body language, and distraction in order to get a target to believe the unbelievable. In short, lying and bending the truth. All Deceit checks are opposed checks against the target's Determine Motive skill. Depending upon the target's beliefs and the plausibility of the lie or bluff, the target will get bonuses or penalties to their check. These modifiers can be cumulative, if such modifiers are appropriate.
Success means that the target either believes the story and does not act unfavorably towards the story because it isn't that important to them. Failure means the target senses something is wrong or that they catch on to the story.