Stands for "Multiple Subtitles" or "Merged Subtitles," meaning the file contains selectable subtitle tracks.
The source of the video. It means the file was recorded/ripped from a streaming service (like Netflix).
The resolution. This is standard definition (SD), which is lower quality than HD (720p) or Full HD (1080p).
The file extension (Matroska Video). It is a popular container format that allows for multiple audio and subtitle tracks in one file. Where to watch it legally