What does alloy mean?

Alloy: actually, it is an ornament mixed with gold and other metals; Zircon: synthetic diamond, a common low-grade jewelry; Occasionally seen in high-end jewelry; Alloy electroplating 18KGP: in popular terms, it is gold with relatively low gold content; How long does the alloy fade: due to oxidation, the alloy gradually fades in about half a year; Diamond: to put it bluntly, it is also a kind of artificial diamond, which is often used in all kinds of low-grade jewelry (occasionally in high-grade jewelry) and high-grade lighting;