All this data is potentially out of date, and should be taken with a truckload of salt
Armor is generally metal plating that is installed on top of a ship's hull. Armor takes all inflicted damaged after the shields have been depleted, although if shielding falls below a certain percentage (25%, reduced by 5% per level of the Tactical Shield Manipulation skill) the ship's armor may take damage.
Many players, particularly those who PvP, use a tactic known as armor tanking, which relies heavily on reinforced and/or resistant armor while ignoring shielding to defend their ship. Gallente and especially Amarr ships specialize in armor tanking, having strong bonuses to ship armor and armor repairing. Some Minmatar ships are also strong armor tankers, but very few Caldari ships can be configured as effective armor tanks.
Some common modules and rigs that affect armor include:
- armor plates - passive increase to armor total, at a cost of additional mass
- energized plating - passive module that reduces damage done to armor.
- armor hardeners - active module that reduces 1 type of damage done to armor by a lot
- damage controls - (cheap) active module that reduces damage to shields, armor, and hull.
- armor repair systems - active module that repairs armor damage to your ship
- remote armor repair systems - active module that repairs armor on other ships