: Specifies the video quality is Ultra High Definition (4K) with High Dynamic Range , offering higher resolution and better color/contrast than standard HD.
: This indicates that the full episode was split into several compressed archive parts (RAR files) to make it easier to upload or download. You would need all parts (part1, part2, etc.) to extract and watch the video. TLOS.S01E01.HMAX.4K.HDR..DxM.part3.rar
: This is the abbreviation for the show title, most likely The Last of Us . : Specifies the video quality is Ultra High