backup : Indicates this is a redundant copy of a primary file, used for data safety or version control.
If you need to upload this to a platform that doesn't support MKV (like some social media sites), you can use a MKV to MP4 Converter to change the container while keeping the video quality intact. prbackup ep 160.mkv
It can store multiple audio streams (e.g., Director's commentary, raw audio, and a final mix) and subtitle tracks in a single file. backup : Indicates this is a redundant copy