: The video compression codec used to encode the file. It is a highly efficient and widely compatible version of the H.264 standard.
: The file extension. Matroska Video (.mkv) is a flexible container format that can hold unlimited video, audio, picture, or subtitle tracks in one file.
: The digital signature or tag of the online group or channel that uploaded or distributed the file.
: The audio format and channel configuration. AAC is a high-quality audio codec, and "5.1" means it supports surround sound (5 normal speakers and 1 subwoofer).