: This indicates that the full download has been split into multiple parts, and this is the third volume in that set. You would typically need all parts (e.g., part1, part2, part3) in the same folder to successfully extract the contents.
Based on the naming convention, here are a few things it indicates: Single.Player.Horror-DARKSiDERS.part3.rar
The text you provided, , appears to be a specific archive filename typically associated with a segmented download of a video game. : This indicates that the full download has