The overall purpose of the digestive system is to break down nutrient molecules that we take in into absorbable molecules to provide energy for our body for growth, repair, movement etc.
The digestion system involves a few steps which includes ingestion, digestion, absorption, assimilation and egestion. Each of every single one of them has an important role in the digestion system.
The digestive system also involves many organs which include oral cavity, esophagus, liver, stomach, intestines etc. Each has important functions too.