Attack roll

An attack roll represents your attempt to strike your opponent. When you make an attack roll, you roll a d20 and add your base attack bonus and your strength modifier. Your dexteritymodifier replaces your strength modifier if you are using a ranged, a thrown weapon or having Weapon Finesse feat and using a proper weapon. If your result equals or beats the target’s Armor Class, you hit and deal damage.

Automatic Misses and Hits: A natural 1 on an attack roll is always a miss. A natural 20 is always a hit. A natural 20 is also a critical threat: a possible critical hit.