[throwup238]

Instead of expending energy to deflect energy weapons fire, the ablative armor undergoes controlled ablation so the outer layers of the armor vaporize or erode when struck by weapon fire, taking the brunt of the attack's energy. This meant that the "total energy" available to defend the ship wasn't limited by the ship's power but by the starbase assembling the ship and the armor could survive a lot more malfunction and battle damage (the shields became completely useless once they burned out). Until the introduction of the armor everyone thought that physical defenses couldn't be used effectively against energy weapons.

Voyager's ablative generator also provided regenerative capability so it didn't need a space dock to repair heavy damage.