: The name of the website or "release group" that uploaded or encoded the file.
Standard players like Windows Media Player often struggle with .mkv files. Use VLC Media Player or MPC-HC for the best compatibility with subtitles and multiple audio tracks.
The phrase "bb-480p-hd-16-oct-desiremovies-mom-mkv" appears to be a specific filename for a digital movie file. Filenames like this typically contain several pieces of metadata used by file-sharing communities: