This is an unusual double extension. A .mkv (Matroska) file is a container that supports multiple audio and subtitle tracks, while .mp4 is a more universal format. Seeing both often suggests the file was renamed or modified for specific player compatibility. Context of the Sources
This stands for English Subtitles included within the file. This is an unusual double extension
Indicates the file contains two separate "original" (official) audio tracks, typically the original English and the Hindi dub. This is an unusual double extension
The original source of the video was a physical Blu-ray disc, which usually implies high visual fidelity. This is an unusual double extension
This was a popular third-party video hosting and file-sharing service frequently used for streaming user-uploaded content.