MKV format debuted in 2002 as a new video container technology. Compared to other video formats, it offered such features as:
Support for embedded subtitles,
Support for multichannel audio,
Original set of codecs.
Matroska codecs became more popular and secure as the technology matured. Currently most operating systems natively supports this video format. Subtitled and audio tracks in MKV containers can be stored separately from video tracks and saved as .MKS and .MKA files for subtitles and audio respectively. However, this is not common. A typical MKV file is single container with all those elements as a single file.
MKV file extension quickly gained large popularity due to their flexibility, high video quality, custom menu support (DVD movie menus), and network streaming capabilities. Initially the MKV format was associated by many with VLC Player, but they are not connected in any way.