When one watches TV, shows and movies are often closed captioned. This is for the hearing impaired, as it provides text on the screen that can be read to relay the sounds and words which they cannot hear. Closed captioning does not display the words until a special decoder for those who need it is detected. Televisions have used such decoders since before the turn of the century.
Open captions operate a bit differently than their closed counterparts, as they are always visible on the screen as part of the programming. Therefore, they require no decoder activation. These captions are connected to the viewing experience and cannot be changed or switched off by the viewr. Anyone watching a program with open captions will always see them.
Subtitling, also known as media captioning when used on the Internet, is used prominently in foreign language films so that people who speak different languages can understand what is being said in their own languages. Subtitles are visible at the bottom of the screen in the translating language. Unlike closed captioning, no special decoder is used for them.
Supertitling often takes place during live performances, such as those seen at the theatre or opera. Supertitling occurs when words are displayed using systems that electronically display them clearly for everyone to see. These systems stand separately from the programming, since the event is live and not on video or film.