Ability DPS: Ability DPS (Damage Per Second) is a measure of the average effectiveness of your hero's abilities. For Offensive Abilities, your Attack DPS is added to this value to determine the damage dealt, whereas Defensive Abilities generally rely only on your Ability DPS.
Will: More Will increases your heros Ability DPS.
Agility: Agility represents you hero's precision, and converts into Critical Hit Chance. However, the higher your hero's level. the tougher enemies become, so you will need more Agility for your hero to keep the same Critical Hit Chance.
Armour: Armour represents the amount of damage your hero mitigates with their gear. As their armour increases, they adsorb a higher percentage of damage from enemy attacks. But, as their level goes up, monsters becomes tough and a higher Armour value is required to have the same percentage of damage reduction
Attack: Attack is a general measure of your heros ability to damage enemies. As you equip weapons and armour that grant higher Attack values, your heros Attack DPS will go up.
Attack DPS: Attack DPS (damage per second) is a measure of the average damage dealt with your characters attacks each second. It is an average value because the actual damage of your attacks will vary based upon the speed of the attack, and the number of targets it is capable of hitting. Additionally, when you use Special Abilities, you Attack DPS is added to your Ability DPS to determine the amount of damage dealt.
Block Value: Block Value represents your heros ability to deflect damage when blocking. Whenever a hero blocks, they will take no damage. But, they loose a percentage of Focus equal to the percentage of health that the damage would have inflicted. Block Value is subtracted from the incoming damage before the percentage is calculated, so having a higher Block Value means you hero can block attacks without loosing as much focus.
Chaos Statistics: There are several Chaos statistics you will find on armour and weapons. There statistics provide you with a chance to inflict an effect on your enemies. The chance to inflict the effect and the duration of the effect are always the same, but the higher the Chaos statistics is, the higher the damage of the inflicted effect.
Chaos: Bloodletting: Grants your attacks the high chance to inflict bleeding wounds on your enemies, dealing moderate damage over 6 seconds.
Chaos Fire: Grants a moderate chance to set your enemies on fire, dealing moderate damage over 6 seconds.
Chaos Ice: Grants your attacks a moderate chance to freeze your enemies, dealing low damage over 9 seconds.
Chaos Lightning: Grants you attacks a small chance to electrocute your enemies, dealing moderate damage over 2 seconds.
Chaos Poison: Grants your attacks a moderate chance to poison your enemies, dealing heavy damage over 9 seconds.
Chaos Vampire: Grants your attack a moderate chance to drain life from your enemies, returning that life to you.
Chaos Weakening: Grants your attacks a moderate chance to weaken your enemies, dealing low damage over 9 seconds and reducing the amount of damage they deal.
Chaos Withering: Grants your attacks a moderate chance to wither your enemies, dealing low damage over 9 seconds and increasing the amount of damage they take from subsequent attacks.
Doom: Grants an additional amount of damage when you critically hit monsters. The amount fo damage is increased with slower attacks.
Momentum: Grants your hero additional Focus when attacking enemies. The amount of focus gained per point of Momentum is based on your level as you become more powerful, you attacks require more Momentum to generate the same amount of Focus.
Retribution: Grants you hero a high chance to deal damage to enemies that attack them. The amount of damage dealt is equal to your characters total Retribution score. Note that Retribution will take effect even against blocked attacks.
Stagger: Chance to stun your enemies. The higher your level the more Stagger you will need to have the same chance to stun an enemy.
Stamina: Hit Points/Health amount.
Warding: Grats the hero a low chance to stun an enemy that attacks them. Again, more Warding is required as you level to have the same chance of stunning enemies. Warding will also take effect even against blocked attacks.
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I am typing this from the 360 menu, so I will keep adding when I can.