Digestion is the process of breaking down food to absorb it. Food is broken down to smaller food particles which are soluble in water. Only then can the food be absorbed into the blood stream.
Digestion occurs in three phases. Mechanical digestion is the physical breakdown of large pieces of food into smaller pieces which can be got at by digestive enzymes. In chemical digestion, enzymes break down food into the small molecules the body can use. Finally, the nutrients are absorbed into the blood stream. Once in the blood stream the nutrients are taken to the liver, which is a kind of chemical factory for the body.