There are various items to be found in the world of Dungeon Defenders. The quality of an item generally determines how good the item will be. The higher quality items have lower drop rates than the lower quality items. The armor types grow stronger the further down the table they are (below). Pristine is currently the highest grade of armor in Dungeon Defenders.
The quality associated with an armor type determines the max stats it can attain. The better the quality, the better the max stats can be. It is possible to have a lower quality item that is better then the next level quality due to overlapping
Level Requirement Chart
The different types of armors have certain restrictions as to how high stats will drop on them. Leather will usually have lower stats then pristine of the same quality. Leather armor can increase resistances as much as plate or pristine.
Resist come in four types: General, Fire, Lightning, Poison. These four allow you to absorb, or negate, damage taken by mobs or players in PvP, thus reducing the total damage taken. A guide is available for more information: Armor Resistance Guide