What is MKV?

The Matroska Multimedia Container is an open standard free Container format, a file format that can hold an unlimited number of video, audio, picture or subtitle tracks inside a single file.[1] It is intended to serve as a universal format for storing common multimedia content, like movies or TV shows. Matroska is similar in conception to other containers like AVI, MP4 or ASF, but is completely open source. Matroska file types are .MKV for video (and audio) and .MKA for audio-only files.

Matroska is an English word derived from the Russian word "matryoshka" (Russian: ????????, IPA: [m??tr?o?k?]), which means "nesting doll" (the common Russian egg-shaped doll within a doll). This is a play on the container (media within a form of media/doll within a doll) aspect of the matryoshka as it is a container for visual and audio data.