Advantage
When luck is on your side: roll two dice and keep the higher one.
Some situations give advantage, for example attacking someone who cannot see you. You roll the twenty-sided die twice and use the higher result. The app tells you when and why it applies.
In Fantasy RPG
Fantasy RPG gives an attack advantage when the attacker is Invisible, or the target is Blinded, Paralysed, Restrained, Stunned, Unconscious, or Prone and attacked up close. Having both advantage and disadvantage cancels out.