Attack Roll. When you make an attack (melee, ranged, or spell), your attack roll determines whether you hit or miss.
Roll + modifiers ≥ target’s AC = attack hits
Roll for damage
Your melee or ranged attack roll is:
1d20 + your ability modifier + your proficiency bonus if you're proficient with the weapon you’re using + any other modifier
Some spells require the caster to make an attack roll to determine whether the spell effect hits the intended target.