MKV Player is a simple video player made primarily for MKV files. This allows you to automatically watch these types of movies with just a double click.
The program, however, has very few options once you run the movie in question. You can simply "play" it "stop" and go back, take a screenshot and do something else.
Whatever it allows you to do, it can easily create playlists from your files, which is especially great if you have a good collection of MKV.
MKV Player is a good video player, which works best as a support for other programs with more applications, as it offers many challenges when trying to play files in formats other than MKV.