Critical threat

A critical threat is obtained when you roll a d20 to hit your opponent and the result (before applying any bonus or penalty) is within the threat range of your weapon, in addition to the modified roll being high enough to hit.

A critical threat means you have a chance to score a critical hit. To do so, a second roll (called the confirmation roll) is made, with the same to-hit bonus being applied, and this roll must result in a hit.