Cochlear implant is a multifaceted research field and clinical concept centered on the investigation, development, and application of neuroprosthetic devices designed to restore a sense of hearing through electrical stimulation of the auditory nerve for individuals with severe-to-profound sensorineural hearing loss. This domain encompasses the study of underlying auditory system physiology and plasticity, advancements in device technology and signal processing strategies, surgical techniques and patient selection criteria, and the efficacy and outcomes of auditory rehabilitation. Its significance lies in its transformative impact on treating profound hearing impairment and its contributions to understanding the neural basis of hearing and neuroprosthetic interfaces.