A refers to a torrent that contains a video file (typically a Blu-ray or 4K UHD rip) where the audio and video streams have been repackaged from the original disc source into a container like MKV without any encoding or quality loss .
A REMUX takes the raw, untouched video and audio streams directly from a Blu-ray or UHD disc and places them into a modern container (usually MKV). Unlike a re-encode (which compresses the video to save space), a REMUX preserves . remux torrent
Here’s a concise piece explaining it: