There are three major differences, even though they may be used interchangeably.
1. Closed Captions are an accessibility feature, making available your video or film available to the Deaf or Hard of Hearing and may include cues as to who is speaking or about what sounds are happening. Like "stomping on the floor". Closed Captioning also makes it easier for those who may not speak English very well this is referred to as internationalization.
2. Historically captions have been embedded within the video and subtitles have been stored externally. 100% accessibility for hard of hearing is mandated by legislation, so captions should always be provided along with the video. Whereas subtitles are only sometimes needed.
3. Sometimes the device or TV will display the captions along with the video and the viewers can turn off or on at any time using the TV itself, but rarely have the option for selecting a language. In these situations when subtitles are added for translation purposes, they are generally hard subtitles and cannot be disabled, however when viewing DVD/Blue-Ray/VOD video, the playback device control whether subtitles are displayed and in which language.
