What exactly does the appendix do and why do you have it?also why do people get it removed?

Nothing: The appendix is just a finger-like projection off the base of the cecum. It has no specific purpose we are aware of. It can become inflamed and swell closed at its base, cutting off its own blood supply through the pressure of the swelling. As it does so it can begin leaking fecal matter and pus into the abdomen. Recognizing the process from the start and removing it before it leaks is needed.