First, an entire audio format called MQA (Master Quality Authenticated) and the company that made it, Meridian Audio. I actually attended one of the presentations for this at RMAF years ago. Basically it is a lossy audio format that was designed to replace FLAC. Now, how does that make sense since FLAC is lossless and MQA is lossy? From what I remember, they purported to bring a real-to-live-performance quality to the audio by also encoding a special "filter" section in parallel to the compressed audio, and when played back on their proprietary (or licensed) hardware, the audio would be decompressed, and then the hardware (which has the proprietary filter algorithms) would apply the special filter section in the recording, to the playback of the track. So basically the benefits would be smaller file sizes (smaller than FLAC, larger than 320 MP3) for your whole collection, and a sort of "guarantee" that each recording you listened to that was MQA certified had been mastered by audio professionals. Surprisingly they got a lot of support initially, they even got TIDAL to offer a bunch of their catalog on MQA. As far as I know now the company still exists but the format is defunct. I can't be bothered to find all of my old articles on it, but there were tons of forum threads and amateur analysis that people did to see if it was better than FLAC, and the conclusion was that unsurprisingly it wasn't.
I remember in the RMAF presentation specifically the guy kept going on and on about the research that went into restoring some Jazz record that apparently had been playing like 5 bpm too fast because the copies of the master tapes that everyone used for vinyl copies (and later CD copies) was played back on the wrong tape machine or something, and they did forensic research to find the original master tapes and the original master tape player they used in studio for the mixdown. Wish I could remember which recording it was.
Here is an article on it I found where you can get a brief history of it.
ARCHIVE.
Tidal also stopped support for the format this year.