OGA is a format of free container audio files, a kind of audio container. The developer is Xiph.Org. The full original name is Ogg Vorbis Audio File. This audio container runs on Ogg Vorbis, a widely used audio encoding and streaming technology. The container stores audio data with compression using Vorbis compression. OGA audio files can also use the .OGG extension because they are a standard Ogg container. Any Ogg-enabled media player must play OGA audio files.
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.