A vegetarian is one who does not eat meat, fish and poultry. A vegan is a vegetarian who refrains from consuming all animal products including milk, cheese, eggs, wool, silk and leather.
The word 'vegetarian' is derived from the Latin word vegetus meaning 'whole, sound, fresh or lively', and its original meaning implies a balanced philosophical and moral sense of life apart from a diet of vegetables and fruits.

• Health reasons - there is evidence of a link between meat-eating and such killers as heart disease and cancer
• Ecological reasons - concern about pollution and degradation of the environment
• Religious reasons - all major religious scriptures condemn killing of any kind
• Compassion for animals - animals too suffer pain and misery when slaughtered
• Belief in non-violence - we must eradicate all thoughts of violence before expecting peace in this world
• Economics - meat feeds few at the expense of many

• Vegan - eats food of plant origin only
• Ovo vegetarian - eats eggs but no dairy products, meat, fish or poultry
• Ovo-lacto vegetarian - eats eggs and dairy products but no meat, fish or poultry
• Lacto vegetarian - eats dairy products but no eggs, meat, fish or poultry
• Pesco vegetarian - eats fish but no meat or poultry (controversial)
• Pollo vegetarian - eats poultry but no meat or fish (controversial)

A vegetarian diet can indeed meet all of one's nutritional requirements.

Good sources of protein include lentils, tofu, low-fat dairy products, nuts, seeds, tempeh and peas.

Many common foods such as whole grain bread, greens, potatoes, pasta, and corn add to one's protein intake.

Plant proteins alone can provide enough of the essential and non-essential amino acids required for growth.

Good sources of iron include dried beans, spinach, chard, beet greens, blackstrap molasses, bulgur, prune juice, brewer's yeast and dried fruit. Foods containing vitamin C, such as citrus fruit or juices, tomato, or broccoli, increase the absorption of iron from a meal. Cooking food in iron utensils also adds to iron intake.

Good sources of calcium include collard greens, broccoli, kale, low fat dairy products, turnip greens, tofu prepared with calcium, and fortified soy milk.

A diet containing dairy products or eggs provides adequate amounts of vitamin B12. Certain fortified foods, such as some brands of cereal, nutritional yeast, soy milk, or soy analogs, are good non-animal sources of vitamin B12.

Good sources of zinc include whole grains, nuts, soy products, wheat germ and legumes.

Most vegetarian diets are generally lower than non-vegetarian diets in total fat, saturated fat and cholesterol. Studies have shown that vegetarians seem to have a lower risk of obesity, coronary heart disease (which causes heart attack), high blood pressure, diabetes mellitus and some forms of cancer.