movie subtitle files “.sub”, “.srt”, “.ssa”, “.ass”
Discovered SubRip. It's a software used to extract subtitles from movie files, by using optical character recognization. Also, it saves its file in a plain text format with suffix “.srt”. This is extremely useful when you want to read the dialog of a movie. The format is supported by most video editors or players, including youtube.
A more advanced but still widely supported subtitle format is SubStation Alpha, with suffix “.ssa” or “.ass”. It is also a plain text format.