Occasionally, you will see touch attacks or ranged touch attacks mentioned in the description or damage description of a spell or feat. But what is a touch attack?

A touch attack is an attack that is successful merely by touching an opponent. This means that things like armor or damage resistance to not count in defense against a touch attack.

A ranged touch attack is much like firing a ranged weapon, where the spell or feat has to be aimed to hit the target. Once again, armor does not matter in the defensive calculation of the attack roll. Most ray or bolt spells will use a ranged attack touch roll to determine success (as opposed to a saving throw).

Both melee and ranged touch attacks use DEX as opposed to STR for their attack rolls.