Gold-filled and gold-plated jewellery both use gold over another material, but they are manufactured differently and should not be confused with solid gold.
Gold plated
A gold layer is deposited onto a base material. Thickness can range from very thin decorative finishes to heavier plating.
Gold filled
Gold-filled products are made by bonding a gold-alloy layer to a core material through a manufacturing process rather than simple decorative electroplating. Exact legal definitions vary by market.
Wear and value
Both can provide gold appearance at a fraction of solid-gold cost. The amount of gold is still far lower than in an equivalent solid-gold piece, so resale and intrinsic value are different.
Read the description carefully
Online listings sometimes mix terms loosely. Look for the base material, fineness of the gold layer, manufacturer information and clear returns policy.