Alchemy is a form of magic which creates magical items which others can use. They typically take the form of potions, or powders, and with the proper formula, are easily reproducible. This means even someone incapable of magic can still perform wondrous feats with the proper knowledge.
The one consistency in every form of alchemy is it involves the transition/transformation of some kind. A healing potion restores someone from a wounded state, while an explosive seeks to transform a living foe into a dead one.
More esoteric alchemists seek to change lead into gold, though they typically meet with failure.
Some typical potions include the following, though the strength certainly varies depending on the alchemical formula used:
A non-potion example of alchemy, this creates a damaging burst to those within its range.
Potion of Health
This potion restores the health of the drinker.
Potion of Vitality
This potion restores the stamina, and spell power of the drinker.
Potion of Haste
This potion increases the speed and reflexes of the drinker.
Potion of Slowness
A potion which causes one's foes to move much more slowly.
Potion of Fear
A potion which, when broken, strikes fear in one's enemies.
Potion of Weakness
A potion which saps the strength of a foe.
Potion of Confusion
A potion which confuses an opponent.
 Seasons of the Wolf Potions
Vial of Distilled Light
A potion which will enlighten you. Imbibing it allows one to always think with a clear head.