Captions
Captions are written descriptions of visual events or speech. Captions permit objects with audio to be "heard" and understood by those who cannot hear the audio. Captioning was primarily intended for those who are hearing impaired but has also been very helpful for those who have normal hearing by visually reinforcing the information. Captioning variants include closed or open captioning, as used in TV's and DVD's respectively. There are also transcriptions, which are descriptive written records of the media and are usually separate from the element itself. Transcribing your media can help all users allowing for indexing and searching.
For more about video captions, see Video and Tools for Captioning and Describing Video.
Example
A screen capture of a video with captions
Links
Captions
(http://www.webaim.org/techniques/captions)
