Strength-based heroes are adept at dealing physical damage to their adversaries. These types of heroes are usually of the warrior or tank class, but this is not always the case.
Intelligence-based heroes use spells to deal magic damage to their opponents. Although these types of heroes are usually supports or mages, they may sometimes fall under a different class.
Agility-based heroes deal physical damage like strength-based heroes do, however they don't deal as much and instead rely on speed and dodging in a fight. These types of heroes are usually classified as assassins or supports, but not always.