Search your "Shared Media" in the specific Telegram chat where you encountered this file to see its original name, context, or thumbnail.
Right-click the file and select "Properties" (on Windows) or "Get Info" (on macOS) to see its size, creation date, and codec information. If you can, try opening the file and letting me know: What is the file size ? (e.g., is it a few KB or many MB?) What content is inside when you play it? Once I have that, I can tell you exactly what it is. AgADpwADnvAQVw.mkv
Use a media player that supports .mkv files (such as VLC Media Player ) to play it and identify the content. Search your "Shared Media" in the specific Telegram