: A compressed archive format. To access the "story" inside, one would typically use software like WinRAR or 7-Zip . Potential Origins
: Many long-running collaborative writing groups archive their sessions. "494_RP" could be the 494th session of a particular campaign, saved for members to read back as a continuous narrative. 494_RP.rar
Do you have on where you encountered this name, such as a specific game or website? : A compressed archive format