Difficulty may also refer to the Difficulty level adjustments to gameplay
Difficulty in a skill check defines the number of successes needed from the dice roll to succeed at the check. It should not be confused with the skill check adjustment, which affects the number of dice rolled. In most skill checks, the difficulty is one (a single success) unless otherwise specified.
The difficulty of closing or sealing gates is normally one. When the Ancient One is Yog-Sothoth or when certain Mythos cards are in effect, the difficulty of closing gates is increased by one, so two or more successes could be required.