Subtitles are texts representing the contents of the audio in a film, television show, opera or other audiovisual media. Subtitles might provide a transcription or translation of spoken dialogue. Although naming conventions can vary, captions are subtitles that include written descriptions of other elements of the audio, like music or sound effects. Captions are thus especially helpful to deaf or hard-of-hearing people. Subtitles may also add information that is not present in the audio. Localizing subtitles provide cultural context to viewers. For example, a subtitle could be used to explain to an audience unfamiliar with sake that it is a type of Japanese wine. Lastly, subtitles are sometimes used for humor, as in Annie Hall, where subtitles show the characters' inner thoughts, which contradict what they were saying in the audio.
Creating, delivering, and displaying subtitles is a complicated and multi-step endeavor. First, the text of the subtitles needs to be written. When there is plenty of time to prepare, this process can be done by hand. However, for media produced in real-time, like live television, it may be done by stenographers or using automated speech recognition. Subtitles written by fans, rather than more official sources, are referred to as fansubs. Regardless of who does the writing, they must include information on when each line of text should be displayed.