If you mean the "No. of Options" when you click the Unique preview in your lobby screen, then it's simply the number of stats that is available in a unique item.
Currently inferno, lightning and dark sets have the highest number in the game (8) and can have the highest value of stats (400 max) including critical damage and attack speed. An item maybe considered excellent if it has lots of blue color but will always be up to the player if he likes the options listed in the item.
This "options" include strength, dexterity, vitality, intelligence, 2 critical stats, attack speed, cooldown duration, & etc. in a sword. Armors includes hp(health) bonus and armor bonus while accessories mainly include resistance bonus and wings is allies bonus. They can be reset and changed for personal preference for about 50 souls.