Protein builds, maintains, and replaces the tissues in your body. Your muscles, your organs, and your immune system are made up mostly of protein. Your body uses the protein you eat to make lots of specialized protein molecules that have specific jobs. For instance, your body uses protein to make hemoglobin (say: HEE-muh-glow-bin), the part of red blood cells that carries oxygen to every part of your body. A majority of protein's are meat. Those include:
Chicken
Steak
Beef
Pork
Those who are vegetarian cannot eat meat. The non-meat choices include:
Fish
Nuts
Beans
Tofu
Soy
Source: kidshealth.org/en/kids/protein.html .To learn more about protein click on the link, or here. On this page, there is additional information on protein not covered here.
This video discusses good form of protein for vegetarians. This is important because many people who do not eat meat, struggle to find foods high in protein. Source: https://www.youtube.com/watch?v=aWM_FgJ4a34