I'm thinking about becoming a vegetarian! Do you know much about being a vegetarian? 
My wife has been one for three years! So, I'm practically one, too. Up front, essentially what it means for your diet is no meat (red meat/poultry/seafood/flesh of any animal), and then also no by-products that are a result of animal slaughter. So, it definitely shortens what you can eat.
Oh wow! It's for a great cause, but it's very limiting. Do vegetarians eat eggs and dairy?
Well, technically some can and do. There are ovo-lacto vegetarians, ovo vegetarians, and lacto vegetarians, with ovo and lacto representing milk and eggs. Three different combinations, where one can eat both, one eats only dairy, and one eats only eggs.
Oh, I see! So I have options! What's the difference between a vegan and a vegetarian?
Vegans abstain from everything. No meat, no flesh, no animal by-products, no fish, no eggs, no dairy. And they also tend to incorporate more of the vegan lifestyle as a philosophy and way of thinking, and not just a diet. It's usually an ethics thing for vegans.
They must really believe in the cause! That's awesome! I'd imagine there are many health benefits to becoming a vegetarian, aren't there?
Absolutely, especially because it encourages the consumption of a lot of fruits and vegetables, which everyone needs. But it also fits seamlessly into a lot of religious practices, like Jainism, Hinduism, and Buddhism, where some forms of animal consumption are forbidden. Vegetarianism has a long history.