Aspect
In Final Fantasy XIV, Aspect refers to the elemental attunement of a crystal or object.
Lore
Eorzea, and the rest of the world known as Hydaelyn, is blessed with a form of magical life-essence known as Aether. Whenever a creature or being dies, its Aether slips from its body and into the next life. Excess amounts of Aether left behind can coagulate into different things : mist, pools, or even crystals. These coagulations attune themselves to specific elemental frequencies. Aether and Aether-created objects can also become corrupted, sapping elemental energies instead of providing them.
Crystals and Usage
When Crafting, elementally aspected crystals are used as catalysts. These crystals are obtained from enemies in the world and from Gathering, and come in various size - Shards being the smallest, and Clusters being the largest.