L’or massif, le placage et le gold filled
The term solid gold indicates that the jewel is made entirely of gold. However, it does not mean that it is made of pure gold. Solid gold can have a variable number of carats: 10k, 14k, 18k, etc. (see article The different types of gold and their classification to learn more about carats).
Gold plating is a thin layer of gold deposited on another metal by electroplating. The minimum thickness of the gold layer is (175 microns). If the plating is thinner, it is called gold wash or gold flash plating.
Gold filled (gold laminate) is the lamination of a layer of gold onto another metal. The layer of gold, which can be a variable number of carats, is fused to a base metal. For example, 14k laminated gold (14k GF), means that the gold layer is 14k. The thickness of the gold layer varies depending on the supplier. It is generally thicker than the plating.