production of saliva
the amylase (which is from the salivary glands) breaking down starch to form maltose in the mouth - this is for carbohydrates
small intestine actually, the first step happens when the food is in the mouth and the saliva is breaking down the food.
Digestion of fats start in the mouth.It is called as mechanical digestion.Later digestion of fats takes place in the intestine
Technacly the first part is when you first take a bite of your meal or the first sip of your drink. This is called ingestion.