The food we eat is digested into small soluble molecules. In the small intestine these solutes arr absorbed into the blood. The villi line the inner surface of the small intestine and are the exchange surface for food molecules.
The villi are finger like projections which greatly increase the surface area for absorption to take place.
The walls of the villi are very thin and there are tiny capillaries close to the wall.
The soluble products of digestion can be absorbed into the villi by either diffusion or active transport.