As its name suggests, an alchemist is basically a researcher who studies the magical effects of elements and chemicals upon people and other things. Alchemy is the subject of transforming one element into another, also known as transmutation. One of the most famous of all transmutations is the ability to transform base metals such as lead into gold.
Alchemists can create things such as potions and poisons. Most of the products of this subclass are battle orientated, and provide either debuffs (such as lowering defense), damage over time (e.g. poisons), and minor buffs to themselves (like a speed boost). Although their creations aren't normally of the healing nature, they are capable of creating minor healing items, although they generally lack potency.