Since the filename itself doesn't describe the video, you can try the following to figure out what it is:

: The .mkv extension indicates it is a Matroska Video file, a high-quality container that can hold video, multiple audio tracks, and subtitles. AgADHwgAArdTsFY.mkv

: Revisit the chat or website where you obtained the file; the surrounding text or "caption" usually provides the context. Since the filename itself doesn't describe the video,