Jewelry listings use a handful of metal terms interchangeably, and they do not mean the same thing. Here is the short version, because it changes how long a piece keeps its color.
Gold plated
A thin layer of gold applied over a base metal, usually brass or stainless steel. It looks like gold and costs a fraction of it. The layer is thin, so how long it lasts depends on how often the piece is worn and what it touches: perfume, lotion, cleaning products, chlorine and salt water all shorten its life. Plating wearing thin is normal use, not a fault.
Gold filled
A far thicker layer of gold bonded to a brass core, rather than deposited as a thin film. It holds its color considerably longer than plating under the same treatment, which is why it costs more. It is still not solid gold.
Sterling silver (925)
Solid metal, not a coating: 92.5 percent silver with the rest usually copper for strength. There is no plating to wear off. It does tarnish over time, but tarnish sits on the surface and comes off with a soft cloth.
Gold over sterling silver
A gold layer over a sterling silver base instead of a base metal. You get the warm color with real silver underneath.
Stainless steel
Solid, hard-wearing and resistant to tarnish, usually finished in a gold, rose or silver tone. It is the practical choice for a piece you push up and down your arm all day.
What we do about it
Every product page on this site states which of these a piece actually is, and we do not describe a plated or gold-filled item as though it were solid precious metal. We do not sell solid gold. Where a stone is cubic zirconia or crystal we say so; those are not diamonds and are not sold as diamonds. The rest is in our Disclaimer.