what does the appendix do?!

Currently - completely useless. Its an old part of the digestive tract that was used for the function of digesting grass and leaves, or plant cells for that matter. Plant cells are surrounded by a cell wall made out of Cellulose or Beta-Glucose which can't be used as regular glucose unless broken down. This is where the appendix came into play as it contains the certain enzymes required to break down the molecules structure.

It was useful back in the day where we had limited food resources and humans travelled around the countryside/landscape in search of food and villages didnt exist - and grass was probably the most abundant food type. The appendix was much larger at this time - as its not been used its essentially been lost and we can no longer digest grass.

Basically nothing they are vestigial organs which mean they have no known bodily function like wisdom teeth, man nipples, and eyes on caved blind fish

It is assumed to have had a function a long time ago. It is a vestigial organ now. Google that.

Not a hella of a lot, since I had it removed!