Matroska Multimedia Container is an open standard free container format. This means that this file format can hold unlimited number of tracks, allowing user to store video, audio, picture or subtitle tracks in a single file.
Matroska file format is primary intended to serve as universal format for common multimedia content as movies or TV shows.
Matroska Video File – MKV, is similar to the .AVI, .ASF and .MOV formats, supports several types of video and audio codec and may also include .SRT, .SSA or .USF subtitles. Because MKV file format supports multiple audio and subtitle tracks in the same file, it becomes very popular in the fan-subbing (subtitle creators) community.