There are four types of armor, some of which are only wearable by certain character classes.
Plate armor is fabricated from metal plate, as the name suggests. It offers the most protection of any of the four armor types against physical attacks. It is very heavy however and is only wearable by Warriors (and sub-classes).
Chain armor is made by weaving steel thread together to make a very strong material. It is lighter than plate, but still offers a medium level of protection. Priests and Scouts can both wear this type of armor (and their sub-classes).
Leather armor is made from animal hides and skins. It offers lower protection than plate or chain armor, but allows the wearer to be much more agile, increasing the ability to dodge attacks completely. Leather armor can be worn by Scouts (and sub-classes).
Cloth offers very little protection from attacks. Mages wear this armor type as it allows them free movement and the ability to concentrate while casting spells.
Abyss Armor is a special type that is available only later in the game. Characters can purchase Abyss Armor using Abyss Points.
Each character has six armor slots in which they can wear armor. Armor can be worn on the head, shoulders, chest, legs, and feet.
Shields are a special type of damage mitigation that are not worn, but rather held in the character's hand. Shields are used to block or deflect incoming attacks. Shields can only be used by the Warrior and Priest classes (and sub-classes).