Let's Start With Some Definitions

Depending on who you ask, there are many different definitions of vegetarianism as well as many different types.

According to The Vegetarian Society:

A vegetarian is someone living on a diet of grains, pulses, nuts, seeds, vegetables and fruits with or without the use of dairy products and eggs.

A vegetarian does not eat any meat, poultry, game, fish, shellfish or crustacea, or slaughter by-products.

Vegetarian Times defines vegetarian cuisine as one resplendent with plant foods -- veggies, fruits, grains, legumes (including soyfoods such as tofu), soymilk and tempeh, nuts and seeds --seasoned with a plethora of herbs, spices and various sauces and pastes such as tahini, and augmented with dairy products and eggs (if desired).

Then there are different types of vegetarians:

Lacto-ovo-vegetarian. Eats both dairy products and eggs. This is the most common type of vegetarian diet. People who eat this way rarely have trouble finding food to eat in restaurants or while traveling. This is a healthy form of vegetarianism as long as you don't overdo it on eggs and high fat dairy.

Lacto-vegetarian: Eats dairy products but not eggs. Many people choose this to lower their cholesterol intake or to avoid an egg allergy.

Ovo-vegetarian: Eats eggs but not milk products. This suits people who have lactose intolerance or have a milk allergy.

Vegan: Does not eat dairy products, eggs, or any other animal product. Vegan recipe books and options are more plentiful now than in the past however eating out may be tricky.

Then there is the flexatarian or the semi-vegetarian. Many argue that there is no such word because you are either vegetarian or you aren't. I use these terms to refer to people who are vegetarian most of the time but occasionally eat fish, poultry or meat. It may also refer to someone who eats fish and/or poultry and avoids meat.