What is the function of gullet in digestive system?

Esophagus

The esophagus, commonly called the gullet, is a muscular tube about 25 cm long, connecting the throat to the stomach. It is lined with mucous membrane, and its walls contain muscular tissue.

The action of swallowing forces the food into the esophagus where sequential, involuntary, peristaltic contractions of its muscular wall propel the food towards the stomach.

Peristalsis is the term given to the passage of food (or fluid) from one end of a tube like structure to the other by a series of waves of contraction. As each new wave of contraction occurs it moves the food a little further along.