Gold-filled and rolled gold are often confused with gold electroplate. Below are the definitions.
Gold-filled is a layer of gold physically bonded by heat and pressure to another layer of metal, normally brass. The layer of gold is much thicker than an electroplated coating. Gold-filled is usually referred to by numbers e.g. 14/20 or 12/20. The first number is the carat of the gold layer, the second refers to the amount by weight of the gold in relation to the base layer. In these examples the gold layer is 1/20th or 5% by weight.
Gold Electroplate or plating is a chemical based process where the article is immersed in a gold containing solution and an electric current is passed through the solution. This causes the gold in the solution to be deposited in a very thin layer on the item of jewellery. Such layers are often minimal and can easily be worn away.
Vermeil is used to refer to silver that has been gold plated.