Digital Audio Tape (DAT) is the recordable version of the CD standard (44.1 KHz/16 bit or 48 KHz/16 bit) that recorded the data onto magnetic tape.
I had two different Sony DAT machines and the quality was very good. As implied by the sampling rates it was CD quality and better. Contrary to popular belief, if you put a warm sounding signal into it, that is what you got back out, but with the limitation of the resolution of the analog to digital converters and the sampling rate.
I mastered a few recording from mutlitrack analog to 48/16 with it in the early 90's.
The main issue I had was the machines were very finicky about being able to play back accurately, the archivability of the medium was very poor for me. I had trouble playing tapes recorded 6 months earlier. Fortunately I was able to direct digital transfers to wave files before I was unable to play the tapes any longer. I even had one machine serviced by Sony and it really still performed the same after.
These were basically miniature rotating head type video playback mechanisms that just stored digital instead of analog signals.