It may be a unique hash or identifier for a specific session or installation. If it is causing an error, please provide the accompanying error message or the software name where it appeared.
MKV (Matroska) files are containers that often hold high-quality video/audio. The most reliable player for this format is the VLC Media Player, which includes almost all necessary codecs. gomk4601mkv
Result? A file often has 15-18% smaller overhead than a standard MKV created from the same source. It may be a unique hash or identifier