The string appears to be a standardized filename for a digital video file, likely sourced from a third-party distribution site. Filename Analysis ep-123 : Refers to Episode 123.
: MKV files often have embedded subtitles. If they don't appear automatically, right-click the video while it's playing and navigate to Subtitle > Sub Track .
: Use VLC Media Player or MPC-HC to play .mkv files, as they natively support the container and multiple audio/subtitle tracks.