Attacks are performed in the following steps:
1. Attack Roll. Attacker rolls a 1d20, adding any proficiency and attack modifier bonuses. Monsters add a flat "to hit" bonus.
2. If the Attack Roll is greater than or equal to the attackee's AC, the attack hits.
3. Damage Roll. Attacker rolls the damage dice associated with the attack and adds attack modifier bonuses. Usually a minimum of 1.
4. Sum of the Damage Roll is subtracted from the attackee's hitpoints.
#tip