There are four different item rarities in the game Common, Magical, Rare and Legendary.

Common items only give you base attributes (Life or Damage) and currently all item types that occupy the same slots have the exact same rolls. Therefore a "Ritual Blade" has exactly the same properties as a "Ritual Blade" and a "Broad Sword"; it seems that base-specific properties have not made it into the Technical Alpha yet. The only difference between two common items is the model.

Magical items have higher base attributes and also have an affix providing a random boost to one of your attributes (Strength, Vitality, Fortitude, Willpower, Intelligence). Additionally magical items can roll Sockets, which can either be socketed with up to Normal Gems of the same color or a Legendary Gem; read more about what gem is eligible in what slot in the Equipment Slots article.

Rare items have an additional magic affix and can roll with up to two attributes. 

Legendary items have all of the above and also a unique legendary effect modifying one of your skills. Legendary items also have Legendary sockets. You can insert Legendary Gems only in these sockets.