What is peristaltic movement and how does it function in the esophagus?

Peristaltic movement is the constriction and relaxation of longitudinal muscles in the gastrointestinal tract in the esophagus, stomach, and the small intestines. It occurs in a wavelike constriction resulting to a process called peristalsis. In the esophagus the movement helps push food in form of bolus (small rounded mass of food) to it.