Six abilities provide a quick description of every creature’s physical and mental characteristics:
Is a character muscle-bound and insightful? Brilliant and charming? Nimble and hardy? Ability scores define these qualities—a creature’s assets as well as weaknesses.
The three main rolls of the game—the ability check, the saving throw, and the attack roll—rely on the six ability scores. The book’s introduction describes the basic rule behind these rolls: roll a d20, add an ability modifier derived from one of the six ability scores, and compare the total to a target number.