You make a single attack that deals significantly more damage than normal.
Prerequisites: Base attack bonus +6.
Benefit: When you use the attack action, you can make one attack at your highest base attack bonus that deals additional damage. Roll the weapon’s damage dice for the attack twice and add the results together before adding bonuses from Strength, weapon abilities (such as flaming), precision-based damage, and other damage bonuses. These extra weapon damage dice are not multiplied on a critical hit, but are added to the total.
Can Vital Strike be used with Spring Attack? Can Vital Strike be used on a charge?
No. Vital Strike can only be used as part of an attack action, which is a specific kind of standard action. Spring Attack is a special kind of full-round action that includes the ability to make one melee attack, not one attack action. Charging uses similar language and can also not be used in combination with Vital Strike.
Pathfinder RPG Core Rulebook. Copyright 2009, Paizo Publishing, LLC; Author: Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook, and Skip Williams.