The Armor attribute on items provides a numerical value that when equipped contributes to the characters Armor Rating. This attribute can be found on Armor items requiring the Light, Medium, Heavy, Adaptive and Droid Armor proficiency. It should not be confused with the Rating value on Armor items, which reflects the items level.
The Armor value on items will vary depending on the slot where the item is equip-able and on the type of Armor proficiency it requires.
Heavy Armor has a higher Armor value than Medium which is higher than Light Armor. Head, Chest and Legs provide about the same amount of Armor for their Rating. While Hands, Wrist, Waist and Feet all provide around the same amount of Armor for their Rating and are a good deal lower in Armor than the Head, Chest and Legs.
For Droid Armor, the Core and Sensor items provide the same amount of Armor for their Rating. The Parts and Motor are also equal with regards to Armor per Rating, and provide significantly less Armor than the Core and Sensor.