: Unlike standard formats like MP4, an MKV file can hold multiple languages or commentary tracks and separate subtitle files that you can toggle during playback.
MP4 vs MKV: Which One Should You Choose for Streaming? - Castr
: To open this file, it is recommended to use the VLC Media Player, as it natively supports nearly all codecs found within MKV containers. Usage Tips
The string appears to be a specific filename or an identifier for a high-quality video file using the Matroska (MKV) container format . File Overview
