You are trained in using your agility in melee combat, as opposed to brute strength.
Benefit: With a light weapon, elven curve blade, rapier, whip, or spiked chain made for a creature of your size category, you may use your Dexterity modifier instead of your Strength modifier on attack rolls. If you carry a shield, its armor check penalty applies to your attack rolls.
Special: Natural weapons are considered light weapons.
If I have Weapon Finesse, can I apply my Dex bonus to my combat maneuver checks instead of my Strength bonus?
It depends on what combat maneuver you’re attempting. Disarm, sunder, and trip are normally the only kinds of combat maneuvers in which you’re actually using a weapon to perform the maneuver, and therefore the weapon’s bonuses apply to the roll. Therefore, if you’re attempting a disarm, sunder, or trip maneuver, you can apply your Dex bonus instead of your Str mod on the combat maneuver check (assuming you’re using a finessable weapon, of course). For other combat maneuvers, you use the normal rule for determining CMB ( Str instead of Dex).
Pathfinder RPG Core Rulebook. Copyright 2009, Paizo Publishing, LLC; Author: Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook, and Skip Williams.