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.
It is intended to serve as a universal format for storing common multimedia content, like movies or TV shows. Matroska is similar in concept to other containers like AVI, MP4 or ASF, but is entirely open in specification, with implementations consisting mostly of open source software. Matroska file types are .MKV for video (with subtitles and audio), .MKA for audio-only files and .MKS for subtitles only.
Matroska is an English word derived from the Russian word matryoshka (Russian: матрёшка, IPA: [mɐˈtrʲoʂkə]), 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.
The loose transliteration may be confusing for Russian speakers, as the Russian word matroska (Russian: матроска) actually refers to a sailor suit.