Mixology is the art of mixing drinks in proper portions and complementary tastes, according to Princeton University's WordNet.
A trained mixologist must create a cocktail that not only tastes great, but also has a pleasing appearance. In addition, a mixologist must choose the right ingredients out of the thousands available to meet each individual's particular taste.
Anyone can mix standard drinks that are enjoyable to the palate, but a mixologist understands how each ingredient in a cocktail reacts to the other, from the combination of liquor and mix to the garnish. A mixologist has mastered both the art and craft of mixing drinks--and can design one-of-a-kind signature cocktails.
Bartending trade organizations, such as the U.S. Bartenders' Guild, are beginning to offer programs that lead to a mixology certification, much like the training a wine connoisseur takes to become a sommelier. Just as chefs are considered culinary artists rather than just cooks, mixologists take the art and skill of mixing cocktails to a higher level. As the American Bartenders School says, "All mixologist are bartenders, but not all bartenders are mixologists."
In addition to obtaining a skill in high demand--expensive signature cocktails make more money for restaurants/bars than food does--many people consider mixology a fine art and receive self-satisfaction from it.