A vegan is someone who, for political, moral, or health reasons, does not eat meat or any animal products such as milk, eggs or cheese.
Omnivore at the next table: I'll have a bacon and cheese omelette and a buttered bagel, please.
Vegans can get a bit overexcited at times.
Most people will assume that because you follow a vegan lifestyle, you must be a pretentious jerk (or in a cult). This is NOT always the case (although you do have your exceptions that give the rest of us a bad name).
Being vegan doesn't mean you have to be a part of any organization (i.e. PETA) or chain yourself up and protest. It just means that you choose to follow a 100% herbivore diet for whatever reason. Choosing to be vegan for diet purposes or animal rights purposes doesn't matter, as long as you're doing it because YOU want to.
If you do it correctly you DO NOT GET SICK and you DO NOT NEED SUPPLIMENTS in order to be healthy and happy. :-.)
John: Would you like to try some teriyaki steak tips?
Jane: No, thanks, I'm vegan. I would love it if you could pass me the tofu fritters though.
John: No, problem. *passes fritters*
THE WORLD CONITNUES UNINTERRUPTED AND NOBODY NEEDS TO STAND ON A SOAP BOX AND BELITTLE EACH OTHER. AWESOME.
Note: Not to be confused with a Nazivegan, who follows a vegan diet but flaunts one's veganhood over everyone else as if it is somehow morally superior. Kinda like saying that a gazelle is morally superior to a lion because the lion is a carnivore, you know? They're not better than each other; just different.