captions

synchronized visual and/or text alternative (opens in a new tab) for both speech and non-speech audio information needed to understand the media content

Note 1: Captions are similar to dialogue-only subtitles except captions convey not only the content of spoken dialogue, but also equivalents for non-dialogue audio information needed to understand the program content, including sound effects, music, laughter, speaker identification and location.

Note 2: Closed Captions are equivalents that can be turned on and off with some players.

Note 3: Open Captions are any captions that cannot be turned off. For example, if the captions are visual equivalent images of text (opens in a new tab) embedded in video (opens in a new tab).

Note 4: Captions should not obscure or obstruct relevant information in the video.

Note 5: In some countries, captions are called subtitles.

Note 6: Audio descriptions (opens in a new tab) can be, but do not need to be, captioned since they are descriptions of information that is already presented visually.

Source: WCAG 2.2 definition of “captions” (opens in a new tab) (W3C)