The provided video explains the topic of achalasia with the help of detailed labeled diagrams with clear narrations. The sub-topics of achalasia covered include: associated normal structure and physiology of upper GI tract and lower esophageal sphincter (LES), misdiagnosis as GERD, pathophysiology behind it, aetiologies, symptoms, investigations required, pseudo-achalasia and different endoscopic, surgical and medical therapies available. Timeline: 0:00 – Overview of achalasia 0:49 – Normal structure and physiology of upper GI tract and LES 3:13 – Misdiagnosis 3:28 – Pathophysiology of achalasia 4:52 – Aetiology 6:08 – Symptoms 6:29 – Investigations 7:10 – Pseudo-achalasia and investigations of suspected pseudo-achalasia 8:16 – Treatment (endoscopic, surgical and medical therapy)