The mouth is where food enters your body just like this gate lets people onto the lawn. The white gate is like teeth because it can block things and open and close.
The esophagus is where food travels using peristalsis. In this picture the blue water slide is the esophagus and the water which represents the food is traveling down.
This picture represents mechanical digestion. The stomach is like the stone in the persons hand grinding the food or the Rock and it turns into chyme which is the dust.