MQA stands for Master Quality Authentication. MQA encodes or "folds" high resolution master source (up to 352.8kHz) onto a CD, allowing any CD player to deliver more detailed, nuanced playback. When paired with a MQA-decoder, MQA-CD unveils the full master quality, high resolution recording.
MQA-CD can be any CD in the family of compact disc such as regular CD, AQCD, HQCDII, UHQCD or Crystal Disc.  Certainly MQA-CD plus Crystal Disc is the best of the best among all the CD formats.