Subtitles are words at the bottom of a movie screen.
In some cases, this is dialogue provided for actors who have been trained to read backwards. This enables a movie to be shot in one or two takes. This is why subtitles are always blurry and dim as they are not intended for the viewing audience.
Otherwise, subtitles are added to translate dialogue into other languages. This is mostly provided for people who know both the spoken language and the translated text. This messes with their brains so that they have to return and pay to watch the movie over again, probably several times. Otherwise, the translated words are used to prank moviegoers, flashing by so fast that nobody could possibly read them.