Subtitles versus Closed caption

Subtitles are pretty much just a translation of the dialog. Subtitles translate the dialogue into other languages so the video can be watched by viewers who don’t understand the language spoken. They communicate solely the dialogue and not the sound effects of the audio track.

Captions are basically just like subtitles except that they include text for both sound effects and dialog. These are typically for the deaf and hard of hearing and are usually required for content on broadcast television. 

Scenarist Closed Captions (SCC) file is required for the implementation of closed captions and Spruce Subtitle file (STL) is required for the implementation of sub-titles.
Captions that are broadcast on television are streamed through the data portion (line 21) of an analog television signal. One method requires turning on closed captions in television settings. The other way is to turn them on or off just like any other subtitles. If the video is meant for broadcast, I believe it is then a legal requirement that they are included in the video stream.

Another term that is used (especially on blu-ray, since they are not capable of carrying the closed caption stream) is SDH or Subtitles for the Deaf or Hard-of-Hearing. It is basically the same thing as closed captions with the only difference being how they are displayed.

Example of Sub-title	Example of Closed caption