Weapons deal different types of damage. Damage and ammunition affinities can be viewed when selecting the weapon in the Inventory (Most Recent Tab).

Enemies have susceptibilities to certain damage types. Exploit an enemy's weakness to gain an advantage on the battlefield.

Armor provides protection based on its Armor values.
Each point of Armor reduces incoming damage by 1, up to a maximum of 60% damage reduction. This maximum can be increased with skills.

There are physical and magical Armor types, each matching the incoming damage types.. Check an item’s Armor values in the Inventory (Most Recent Tab).