Apple uses the term VoiceOver for the audible assistance in navigating the menus, for the visually impaired.
The narration of scenes during content playback is referred to as Audio Descriptions. That is a separate audio track, similar to a different language.
These are different functions with each their own on|off setting.
Settings﹥Accessibility﹥VoiceOver﹥VoiceOver﹥On|Off
Settings﹥Accessibility﹥Audio Descriptions﹥On|Off
One or both of these may have been activated accidentally through the Accessibility Shortcut (triple-click Menu or Back). The Accessibility Shortcut switches on or off one or more pre-defined accessibly functions. Each of the possible accessibly functions can be included or excluded in the shortcut. De-selecting all functions disables the shortcut.
Settings﹥Accessibility﹥Accessibility Shortcut﹥…