09 (b-global 1920x1080 Hevc Aac Mkv) [666... — [ ] -

: This is the File Container (Matroska). Unlike MP4, MKV can "wrap" multiple audio tracks and subtitle files into a single file, making it the preferred format for the anime community.

Each segment of the name provides specific information about the media file: [ ] - 09 (B-Global 1920x1080 HEVC AAC MKV) [666...

: This is the Audio Codec (Advanced Audio Coding). It is a standard lossy compression for digital audio designed to be the successor to the MP3 format. : This is the File Container (Matroska)