In Burning Crusade Classic hunter pets benefit from 'pet scaling'. This just means that your pet gets to add some of your stats to their own stats, so that their power scales with your power. The basics are very simple:
Pets get about 30% of the hunter's stamina added to their stamina.
Pets get about 35% of the hunter's armor added to their armor.
Pets get about 22% of the hunter's ranged attack power added to their melee attack power.
Pets get about 12.5% of the hunter's ranged attack power added to their spell damage.
Pets get about 40% of the hunter's resistances added to their own resistances.