Audio Description
Audio Description (AD) provides descriptive narration of key visual elements that make visual media inclusive. It takes a video and talks you through it by describing elements such as actions, gestures, scene changes, images of text important to understanding, and any other significant visual information. It makes video and multimedia accessible by capturing what is happening on screen into audible descriptions that are incorporated during natural pauses in the sound track. It provides a mental picture of what is happening.
Captioning
Captions are synchronized visual and/or text alternative for both speech and non-speech audio information needed to understand the media content. They are synchronized with audio or video. Captions include dialogue and, unlike subtitles, also identify who is speaking. They convey information about spoken words and non-spoken sounds, such as music or sound effects. Captions benefit people who are Deaf or hard-of-hearing, and anyone who cannot hear the audio (e.g., someone in a noisy environment). Captions are generally rendered graphically above, below, or superimposed over video.