Dear student,
Tonsils are the types of lymph glands on both the sides of throat. They are a part of immune system as they act as first line of defence against infection of the throat. The infection of tonsils is called tonsillitis. It results in swelling in tonsils. Tonsillitis happens when tonsils are infected either by bacteria or viruses. They may become red and swollen and in the worst conditions, they may have pus inside. As the body develops it will find the other ways of fighting infection this causes the tonsils to shrink with the age.
Regards.