Disadvantage
When things are against you: roll two dice and keep the lower one.
Some situations give disadvantage, for example shooting at a target very far away. You roll the twenty-sided die twice and use the lower result. The app tells you when and why it applies.
In Fantasy RPG
Fantasy RPG gives disadvantage to attackers who are Blinded, Frightened, Poisoned, Prone or Restrained, against invisible targets, against Prone targets from range, and at long range. Restrained creatures also have it on Dexterity saves.