One of the important things about being a vegetarian is what you eat. Just because you don't eat meat or, if your a vegan, dairy, makes you a vegetarian. What matters is what you put in to yourself. If you don't put the right amount of nutrition in your body, then you won't get the things you need to live a healthy life style. 

You can't eat fries, or something like nachos. This isn't healthy for your body. 

Vegetarians need to careful about what they do and don't put into themselves. 

To be a vegetarian, you have to make sure to get enough vitamins and minerals, but most importantly protein.