Peroral endoscopic myotomy (POEM) is a minimally invasive endoscopic procedure used to treat achalasia, a swallowing disorder caused by the failure of the lower esophageal sphincter to relax. During the procedure, an endoscope is inserted through the patient's mouth and into the esophagus, where muscle layers are cut to allow the lower esophageal sphincter to open more easily, improving swallowing function.