MKV is an open container format for audio and video data created by Russian developers. The name of the format originates from the name of the project - Matroska (Matryoshka) with the addition of the first letter of the word Video. This format is considered an alternative to the much more popular AVI, but has not yet reached such a scale of distribution. MKV files are quite common among owners of fairly old mobile devices with Symbian OS and at the same time among those who prefer to watch video in FullHD, since MKV has good dynamics of transmitting video / audio streams. MKV with a wide range of features, in particular, storing audio tracks in different languages, is easy to edit, there are no freezes in large files.
M2V is a video category file format, also called MPEG-2 Video. It supports video with a tighter time constraint and interlaced display. The encoded speed at which data is transmitted may be of the order of 40 Mbps (for storage and transmission). It may be higher for professional use in video production. Large frame sizes do not support HD resolution. MPEG-2 format is compatible with MPEG-1. The MPEG-2 format is used mainly for the consumer level of video broadcasting - for example, DVB. And for storage - for example, DVD. But they are also used for professional applications. Say for storing video in a studio. Files with the extension .m2v are necessary if you are preparing a video for burning to DVD using specialized programs. There will be no sound in such a file. This encoding method also involves the .m2a file, where the sound is stored. Then this pair of files (.m2v and .m2a) will be sent to the authoring program line. The program will output them without recoding in the program stream (MPEG 2 PS). There is one caveat. When the weight of these files is 4.3 GB or more, then you need to transcode this file and reduce the bitrate. So when you create * .m2v, you must first select the correct bitrate.