The feature, which is supported on iPhone 12 and later, is described by the company as a method by which Deaf and hard-of-hearing people can “experience music on iPhone with taps, textures, and refined vibrations that are synchronized with a song’s audio.”
Music Haptics, which has a corresponding API for App Store developers to hook into their own apps, works over Wi-Fi or cellular connections and obviously is supported by Apple Music, Apple Music Classical, and the Apple-owned song identification service Shazam.
(Forbes)