There are numerous subspecies of vegetarian:
There are fruitarians, who only eat the fruits of plants, so as to not kill the plant by eating it.
There are raw foodists, who do not cook anything over 120 degrees F. (Some of these folks include raw meat in their diet. There is a big movement of these folks in France.)
A vegan is one who only eats and wears materials derived from plant and artificial sources (no insects, animals, reptiles, etc). Hoepfully many vegans would eschew the artificial additives and artificial foods, but it is not a requirement.
Many vegans include Brewers Yeast in their diet, yet I am told that this is a single celled animal. Hypocritical? I donno.
A vegetarian, typically, consumes animal derived milk and eggs, in addition to vegetable based foods. Typically, this person would be called a lacto (milk) ovo (egg) vegetarian.
Ergo, a Lacto-vegetarian consumes milk products and vegetable based products.
An Ovo-vegetarian consumes eggs.
A pesco vegetarian, arguably not a vegetarian, is one who consumes fish, in addition to vegetable matter.
To make matters more confusing, vegetarian, as it is commonly used, is improperly refering to people who only eat vegetables. The name was taken by a group in the early 1850's in England. Based on the Latin word "Vegetus," meaning "lively and full of life," it was not intended to infer abstinense from meat.
steve shapiro winner, 1995 Vegetarian Times Trivia Contest & former co-director of the Vegetarian Society of Houston, a vegan organization.