Metals Primer (as it relates to jewelry, not car repair!)
Understanding the difference between gold, gold-filled, gold-plated, gold-electroplated, gold-overlay (vermeil) or gold-finished is important when you're considering a piece of jewelry for yourself or as a gift.

Karat gold typically comes in 10K, 14K, 18K, 22K and in some cases 24K for jewelry applications. This means the jewelry is a true alloyed gold that will stand up to the wear and tear of everyday use. Higher-karat gold includes less alloy metal (24 karat is pure gold), so it's softer and may not be appropriate for high-wear pieces such as rings.

Gold-filled is heat- and pressure-bonded gold (5% by weight) over a base metal sheet or core.

Vermeil is 100 millionths of an inch of gold electroplated over sterling silver.

Gold-plate and gold-electroplate are two terms for the same material: this process involves coating metal (usually brass) with a microscopic coating of gold which eventually wears to expose the base metal underneath.

Gold finish (or yellow finish) indicates the piece has no real gold content, but a gold color. A piece indicated as gold color may not even be made from metal—it could be plastic with a gold-color finish on it and still be called gold finish.