The simplest definition of vegetarianism is a diet free of meat, fish, and fowl flesh. But eating habits of vegetarians cover a wide spectrum. At one end are lacto-ovo vegetarians, who avoid animal flesh but eat eggs and milk products. At the other end are vegans, who forgo eating (and often wearing) all animal-based products, including honey.
There are also pescatarians, who eat fish and seafood; and lacto-vegetarians, who eat dairy products but not eggs. Fruitarians follow a diet that includes fruits, nuts, seeds, and other plant food. Those who follow a macrobiotic diet eat mostly grains but can also eat fish.
Vegans and ovo-vegetarians, who eat eggs but not dairy, need to find foods (dark green vegetables, tofu, edamame, soy nuts, butternut squash, calcium-fortified non-dairy beverages) or supplements that compensate for the missing calcium from their diets. Absorbable calcium is critical to protect against osteoporosis, or thinning bones.
A vegan diet includes all grains, beans, legumes, vegetables and fruits, and the nearly infinite number of foods made by combining them. In addition, many vegan versions of familiar foods are available, so you can eat vegan hot dogs, ice cream, cheese, non-dairy yogurt and vegan mayonnaise along with the more familiar veggie burgers and other meat substitute products.