"These [RTS files] first premiered in Rise of the Triad, and really took off in popularity with the release of Duke Nukem 3D. I assume they will continue to be used in many of Apogee's and 3D Realms' games. They are used predominantly in Multi-playing as ways to express yourself about something that happened, or is about to happen. The majority are humorous in nature, but a few have ventured into making a serious file with a real purpose."

-- Charlie Wiederhold, Official RTS FAQ