There are two main reasons why people are vegetarian. The first one is because they do not want to kill animals and the second one is because of religion. But which religions and why? Well, in Hinduism, they cannot eat beef as the cow is their sacred animal however, strict Hindus are vegetarian because they believe that every animal is sacred. Many Budihsts are vegetarian or vegan but I could not find out why. Muslims also have very strict dietry laws: they cannot eat pork in any form and also have strict rules on fish (they cannot cut off the fins and scales). These are the religions that have the most dietry rules but many other religions also have some food restrictions such as Judaism and Christianity.
I also found out that there were three types of vegetarians. Ovo-Vegetarians eat only eggs and plant foods, Lacto-vegetarian eats dairy foods and plant foods and Vegans or strict vegetarians eat only plant foods and products.