"Dual Audio" means a single video file contains multiple audio tracks, usually the original language (English) alongside a dubbed version (like Hindi, Spanish, or French). This lets you choose which language you want to hear without downloading separate files. The audio track is selected in your video player's settings. The original Blu-ray release of Dumb and Dumber To , for instance, contains an English 5.1 track as well as dubbed French and Spanish audio.