Many people are familiar with closed captioning, the means by which the dialogue and sound effects of a film or television program are made visible via on-screen text. However, description, for viewers who are blind or have low vision, is less familiar. Description conveys the key visual aspects of a film or television program by describing scenery, facial expressions, costumes during natural pauses in dialogue.
You can listen to a clip of Disney's The Lion King with descriptive narration
created by The Media Access Group at WGBH. Because people who are deaf or hard of hearing have few opportunities to "experience" description, this clip also has closed captioning.
Audio Description Project - This site contains extensive information about audio description, from what is it, to samples, to who does it, to how and where it is available in various media. (An initiative of the American Council for the Blind.)
Several television networks, including ABC, CBS, Fox, and TNT, have each added approximately four hours a week of described video programming. (October 17, 2012)
These accessible offerings are required under the Twenty-First Century Communications and Video Accessibility Act (CVAA). For more information on the CVAA, a list of described programs, and instructions for accessing described video, visit the FCC audio description page.