Villi are finger-like projections that can be found in the small intestines. Their function is to increase the total surface area over volume ration so the digested food can be absorbed faster and more efficiently.
The first photo shows the villi of a healthy colon (20 000 magnification)
The second photo shows defective villi. You can see the villi are covered with sticky mucus and surrounded by bacteria so that a normal movement is no longer possible. (50 000 magnification).