What are the sites of nutrient digestion and absorption in the human GI tract?
The saliva from your mouth will slowly start to digest starches.

Then the stomach specializes in digesting protein with enzymes and its highly acidic content. 

The small intestine will digest proteins, starchs and carbs (with the help of the enzymes traveling from the stomach).

The liver and pancreas secretions will join in the small intestine will help break down fats and complete digestion.

The small intestin is responsible of absorbing the vast majority of digested nutrients and the water is then mostly absorbed by the colon.

Source: Your Digestive System and How It Works