Warcraft III armor and attack types

In Warcraft III, Units have Armor and Attack types that modify the damage they deal/take against other units.

Normal

 * Mainly used by melee or short ranged units. Effective against ground ranged units.
 * Examples: Knights, Huntresses

Piercing

 * Primarily used by ranged attackers, ground, air, or structure. Effective against aerial units and spellcasters.
 * Examples: Crypt Fiends, Hippogryph Riders

Magic

 * Primarily used by spellcasters, but also by certain heavy air units. Effective against heavy infantry and cavalry. Introduced in patch 1.06.
 * Examples: Druids of the Talon, Gryphon Riders

Siege

 * Used by siege units, to destroy fortifications and spellcasters.
 * Examples: Meat Wagons, Mortar Teams

Hero

 * Used by Heroes. Full damage to all units except those with Fortified armor.
 * Introduced in patch 1.06.

Chaos

 * Used by powerful creeps, generally level 7 and higher. The Black Citadel and Outland tilesets contain creeps below level 7 capable of using chaos attacks. Full damage to all armor types.
 * Used in the campaign by Chaos orcs, as well as high-ranking demons and demigods.
 * See also: Chaos (spell school)

Heavy

 * Primarily used by melee units, long-ranged siege weaponry, and summoned units.
 * Examples: Druids of the Claw, Demolishers

Medium

 * Primarily used by ground ranged units.
 * Examples: Riflemen, Spell Breakers

Light

 * Used by most air units, and Scout Towers for whatever reason.
 * Examples: Destroyers, Frost Wyrms

Unarmored

 * Mostly used by spellcasters, and certain air units. Equally vulnerable to all types of attack.
 * Examples: Necromancers, Gargoyles

Fortified

 * Used by most buildings.
 * Also used by Siege Engines.

Hero

 * Used by Heroes.
 * Resistant to most types of damage, except for Normal and Chaos. Takes 70% damage from Spells.

Divine

 * Used by powerful characters in the campaign.
 * Divine beings take only 5% damage from attack types other than Chaos, and only 50% damage from spells.

Reign of Chaos
In Reign of Chaos, Heavy, Medium, and Light armor have rotated. So Light takes extra from Normal, Medium takes extra from Magic, and Heavy takes extra from Piercing.

Also note basic melee units such as Grunts have Medium armor, but heavy melee such as Tauren have Heavy armor. Summons and Workers also have Medium armor.