Cue the Wikipedia definition (with minor changes): “Subtitles for the deaf or hard-of-hearing refer to regular subtitles in the original language where important non-dialog information has been added, as well as speaker identification, useful when the viewer cannot otherwise visually tell who is saying what.”

We consider them a hybrid between subtitles and closed captions: They are displayed in the format of subtitles and with its technical characteristics (e.g., two lines, all centered), but contain many elements present in closed captions (e.g., sound descriptions, speaker identifications, intonations.) They are a very effective way of creating subtitles that are accessible for deaf audiences and that also benefit students of the language. Unlike proper closed captions, they can be viewed without the need of a decoder, and are cheaper and faster to produce.