Intellect reduces the cooldown time of Super Charged Abilities, allowing you to use them more often. Find and equip armor with Intellect to boost this effect. 100% Intellect will reduce your Super's cooldown from 5:30 to 3:55. You will also receive double the Super energy from kills.
Discipline decreases the cooldown time of your grenades, allowing you to use them more often. Find and equip armor with Discipline to boost this effect. Grenades take 60 seconds to cooldown, With 100% effectiveness this goes down to 20 seconds. 270 Discipline seems to be the cap for 100% effectiveness.
Strength reduces the cooldown time of your Throwing Knife, Storm Fist & Energy Drain, allowing you to use them more often. Using your melee while charged adds a damage\elemental bonus to the melee attack. Like the grenades it takes 60 seconds to cooldown. Strength decreases the cooldown period and at 100% effectiveness, it's 20 seconds. Again the cap seems to be 270 strength to max out the effectiveness.
Secondary stats in Destiny affect a player's damage taken, health regeneration and movement speed. Unlocking certain abilities will increase these stats, making a player harder to kill. These stats are:
Increases the amount of damage you can take before dying.
Increases the speed at which you regain lost health
Increases your movement speed and maximum jump height.