The source of the video, typically losslessly ripped from a streaming service like Netflix or iTunes. The video compression codec used (H.264). ESub
: This could refer to the source or the uploader, possibly "KickassTorrents," which was a popular torrent site before it was shut down. However, it might also refer to another torrent site or service.
, appears to be a specific release filename for a movie or digital media file.