A character can choose to activate the Acrobatics ability to attempt to use their Mobility skill to move through areas threatened by enemies without provoking an Attack of Opportunity. You’ll find the Acrobatics ability in the Abilities tab (the middle tab) above the action bar, and it can be toggled on and off at will. A character using Acrobatics moves at half speed, but if they succeed at a Mobility (DC 15) check they’ll avoid provoking an Attack of Opportunity.