Artisan crafting materials are important, very important. Players need to amass thousands of these items by playing Diablo 3 for hours on end. Usually players do not collect all the materials they need on their own but instead trade with others to get what they need. This can be done with real money on the RMAH or through gold earned by trading items that they have earned. Long story short, crafting materials are the bread and butter of artisans and crafting.
Types of Crafting Material
ALL crafting materials are acquired by salvaging existing armor and weapons. The quality of the weapon or armor piece will determine the quality of the salvaged good. It works like this:
Magic Weapons & Armor (blue quality) -> Essences
These essences include the Subtle Essence, Shimmering Essence, Wishful Essence and the Exquisite Essences found in Diablo 3.
Rare Weapons & Armor (yellow quality) -> The animal parts
I call these the animal parts (lacking a better name for now), they include the the Fallen Tooth, Lizard Eyes, Encrusted Hoofs and Iridescent Tears.
Legendary Weapons & Armor (orange quality) -> Bark, ash, coal and brimstone
These could be called the elemental components to crafting. They include the Petrified Bark, Corpse Ash, Volcanic Coal and Fiery Brimstone. These are mega valuable, the most sought after trade goods in Diablo 3.
Where to find them
It is very easy to know what to expect when salvaging gear. Based on the difficulty that you acquired the gear in:
Normal -> Subtle Essence, Fallen Tooth and Petrified Bark
Nightmare -> Shimmering Essence, Lizard Eyes and Corpse Ash
Hell -> Wishful Essence, Encrusted Hoofs and Volcanic Coal
Inferno -> Exquisite Essence, Iridescent Tears and Fiery Brimstone