A gold compact disc is one in which gold is utilized in place of the high-purity aluminium or silver commonly used as the reflective coating on ordinary CDs and CD-Rs respectively.
Gold disks are available as both CDs and CD-Rs as well, and are compatible with standard players and recorders.
The advantage of the gold reflection layer lies in its corrosion resistance.
As such, gold CDs were seen as a potential solution to the incidence of CD rot on early CDs (mainly manufactured by PDO UK).
[1] In 2014, Audio Fidelity, an American publisher of audiophile CDs, announced that it was abandoning the gold format and moving to the hybrid Super Audio CD (SACD) format for future releases.