Achalasia is a rare esophageal disorder characterized by the inability of the lower esophageal sphincter to relax, leading to difficulty in swallowing (dysphagia), regurgitation, and chest pain. This condition occurs due to the degeneration of nerve cells in the esophagus, affecting its ability to move food toward the stomach. Symptoms typically develop gradually and can significantly impact a person's quality of life. Treatment options include medications, balloon dilation, and surgery to improve esophageal function.