What is the muscular valve between the esophagus and the stomach

The lower esophageal sphincter, or gastroesophageal sphincter

Explanation:

The esophagus is a structure, part of the alimentary canal (gastrointestinal tract) that connects the pharynx to the stomach and through which the food passes. The esophagus is a fibromuscular tube that is involved in the food transport via peristaltic contractions (radially symmetric muscle contractions and relaxation).