Esophagitis is inflammation of the esophagus that can have various causes like acid reflux, infections, medications, radiation, and more. Common symptoms include dysphagia, heartburn, and painful swallowing. Diagnosis involves endoscopy and biopsy. Treatment depends on the underlying cause but may include lifestyle changes, antacids, H2 blockers, proton pump inhibitors, and surgery in some cases. Complications can include strictures and Barrett's esophagus.