This means the file was losslessly ripped directly from a streaming service like Netflix. It usually offers better quality than a "WEBRip."
(Implied by the "x...") This refers to the video compression. x264 is standard compatibility, while x265 (HEVC) provides better quality at an even smaller file size.
This subject line indicates a video file for the first season of the popular TV show ( La Casa de Papel ). S01: Season 1.