The filename is cut off, but the full file would likely end with something like .mkv or .mp4 .
This refers to High Efficiency Video Coding. It is a modern compression standard that allows the file to maintain high visual quality while keeping the file size much smaller than older formats like x264.
For cinephiles and home media enthusiasts, the film is a frequent choice for high-quality encodes (like the 1080p HEVC x265