In starship combat, "critical hits" allow you to do more damage to the enemy ship.
Critical hits are influenced by two starship statistics: critical rating (also called critical chance) and critical bonus. Crit Rating determines how likely it is that your ship scores a critical hit, while Crit Bonus determines how much extra damage your critical hits do. In general, Crit Bonus and Crit Rating do not increase with ship level. They are inherent to the ship class. Crew equipment, however, and crew abilities can grant ship bonuses that sometimes substantially increase these stats.
Crit Rating or Crit Chance determines how likely it is that your ship scores a critical hit. Your rating translates directly into how likely it is that every shot your ship makes is a critical hit, which does extra damage. For example, a ship with a Crit Rating of 1000 (for instance the Ferengi D'kora Marauder) has a 10% chance of scoring a critical hit. As your crit rating increases, the chance of you scoring a critical hit goes up as well.
Crit Bonus determines how much extra damage your critical hits do. A Crit Bonus of 10,000 will result in double damage on a critical hit. Increasing your crit bonus will increase the amount of extra damage your attacks do when they land a critical hit. To calculate your extra damage, take your crit bonus and divide by 100. The resulting number is the amount of extra damage your shots will do when they critically hit.
For example, the Prakesh has an attack potential of 7525 and a Crit Bonus of 8000‱ (i.e. 80%), so any critical hit will inflict 6020 additional points (80% of 7525), bringing the total damage to 13545 (minus some rounding error).
Critical hits can double the hits from your ship, and are thus very powerful.
Powerful characters can add hundreds, up to thousands, of critical rating and critical bonus points. The critical rating adds a 10% chance for every 1000 points. The critical bonus doubles the damage for every 10000. Therefore, both can make a noticeable difference in the performance of a starship and the outcome of a battle.