What's the difference between strep throat and tonsillitis?

Strep throat: Tonsillitis is a generic term that describes an irritation/inflammation of the tonsils. Tonsillitis can be caused by infectious bacteria or viruses strep throat refers to the bacterial organism sometimes responsible tor tonsillitis. It is characterized by beefy red, ulcerated, very painful tonsillitis. Strep throat remains the most common reason for removing the tonsils.