Karaoke is a Japanese sing-along game in which lyrics are displayed on a screen in order for someone to sing along to a song that has been stripped of its lyrics. But what does this have to do with your files?
Karaoke information is mostly found in video files or audio files that have been derived from videos containing such information. Similar to subtitles, Karaoke information is typically displayed as text. The text contains the lyrics of the song contained in the video and can be visualized in different ways. For example as a text crawl (cf. The intro to Star Wars) or lighting up or changing color when certain parts should be sung.