This indicates that "English Subtitles" are included (hardcoded or muxed into the file). .mkv: The file container (Matroska Video).
The source website or the "tag" of the group that encoded and uploaded the file. 720p: The resolution (High Definition).
This filename follows a standard format used by online media release groups. 720p: The resolution (High Definition)
This version contains scenes that may have been cut from the original theatrical or broadcast version.
Likely a unique release ID or internal code for the uploader/group. Likely a unique release ID or internal code
The source of the video was a high-definition digital stream or file.
The video codec used (High Efficiency Video Coding). This means the file is compressed to be small without losing much quality. 720p: The resolution (High Definition)
The language of the audio or the specific regional version of the content. S01E01: Season 1, Episode 1.