subtitle

A heading below or after a title.

Textual versions of the dialogue in films (and similar media such as television or video games), usually displayed at the bottom of the screen.

Careful viewers have long observed that in the movies, one can not only watch but read cigarettes like subtitles — translating the action on the screen into another language which the camera registers but rarely foregrounds, a part of the thickness of the medium which is almost never brought into focus. […] The cigarette in the scene serves as a subtext, a mute caption or subtitle, sometimes accompanying, sometimes contradicting or diverting the explicit premise of the action or the open meaning of signs.

To create subtitles for the dialogue in a film.