Achalasia is a rare disorder of the esophagus that results from damaged nerves that control food movement. It causes difficulty swallowing and food getting stuck. The document discusses the causes, symptoms, tests used to diagnose (endoscopy, manometry), and treatments of achalasia. Treatments include medications to relax muscles, botox injections, balloon dilation procedures, and surgeries like Heller myotomy to cut the lower esophageal sphincter muscle.