This is the High-Efficiency Video Coding standard. It allows the file to maintain incredible detail while being significantly smaller than older x264 files. It’s the reason you can fit a high-def season on a hard drive without sacrificing the cinematic look.
A: The keyword doesn't specify, but most "top" releases use DTS-HD Master Audio (lossless) or high-bitrate AC3 (Dolby Digital) @ 640kbps . Check the full release notes. DTS-HD is superior but larger in size.
: The source material. This indicates the file was "ripped" from an official physical disc, ensuring the highest possible starting quality.