The tonsils are two small masses of lymphoid tissue located at the back of the throat, one on each side. They are part of the immune system and play a role in fighting off infections that enter the body through the mouth and nose.
The tonsils can become inflamed or infected, resulting in conditions such as tonsillitis. While they can be removed if they become infected, they do serve a purpose in the immune response.
Further Reading:
Immune System Structure, Function, & Health Tips