This means the file was sourced directly from a streaming service (like Netflix or iTunes), ensuring high quality without the "compressed" look of a disc rip.
Likely the "release group" or the person who encoded the file. How to "Install" or Play an MKV File blockz2020720pwebdlaacx264mkvking install
To "install" these, right-click the folder and select using a tool like WinRAR or 7-Zip. This means the file was sourced directly from