Some features and effects let you roll with advantage or disadvantage on an action or reaction roll:
- Advantage represents an opportunity that you seize to increase your chances of success. When you roll with advantage, you roll a d6 advantage die with your dice pool and add its result to your total. - Disadvantage represents an additional Difficulty, hardship, or challenge you face when attempting an action. When you roll with disadvantage, you roll a d6 disadvantage die with your dice pool and subtract its result from your total.
Advantage or disadvantage can be granted or imposed by mechanical triggers or at the GM's discretion. When a PC aids you with Help an Ally, they roll their own advantage die and you add it to your total.
Advantage and disadvantage dice cancel each out, one-forone, when they would be added to the same dice pool, so you'll never roll both at the same time. If you have advantage or disadvantage from other sources that don't affect your own dice pool, such as another player's Help an Ally move, their effects stack with your rolled results.