This document details otitis media, including its epidemiology, classification, etiology, treatment, and the middle ear ventilation system. Otitis media is common in otology, with high childhood incidence—nearly all children have it by age three. It causes high US medical costs and is a top cause of pediatric acquired hearing loss, more prevalent in winter, in males, Native Americans, and Alaska Natives, with social hygiene affecting chronic cases. China’s 2004 guidelines categorized chronic suppurative otitis media into three types, and the 2012 version separated middle ear cholesteatoma; “osteitis type” is internationally called “chronic mastoiditis.” Etiologies include Eustachian tube dysfunction, infection (biofilms exist, PCR detects more pathogens than culture), and gastroesophageal reflux. The middle ear ventilation system (Eustachian tube, tympanic membrane, mastoid, etc.) is key. Treatment focuses on antiinfection and drainage; surgery improves ventilation but tympanostomy tubes have drawbacks. It also clarifies misconceptions, like Eustachian tube status not affecting tympanoplasty efficacy, and stresses mastoid exploration in tympanic membrane repair.