Some features let you roll with advantage or disadvantage on an action or reaction roll:

Advantage represents an opportunity, through either magical or mundane means, that you seize upon to increase your chances of success. When you roll with advantage, you add a d6 advantage die to your total.

Disadvantage represents an additional difficulty, hardship, or challenge you face when attempting an action. When you roll with disadvantage, you subtract a d6 disadvantage die from your total.

Some of your abilities may automatically grant you advantage or disadvantage, but the GM can also choose to give it to you for any roll where it fits the story.

The d6 you roll should be a special color so it’s not confused with any d6s you roll for other effects; this allows you to easily spot your disadvantage d6 and subtract it from the result. However, you only need one d6 for rolling both advantage and disadvantage, because you’ll never roll both at the same time: Advantage and disadvantage always cancel each other out when applying to the same roll. If, for example, the GM gives you disadvantage on a roll, but you gain advantage from a domain ability, the two cancel one another out. If you have two sources of advantage and one of disadvantage, you instead only have advantage.

NPCs can also roll with advantage (or disadvantage), but when they do, the GM uses rolls an extra d20 and picks the highest (or lwest) result (See “Giving Advantage and Disadvantage” in chapter 3).

Tip: Some moves or effects require you to add or subtract a d6 for reasons other than advantage or disadvantage. If you find yourself both adding and subtracting a d6 for any reason, you can simplify your roll by rolling neither, since they cancel each other out as if they were advantage and disadvantage.