Gold-filled is a type of metal that is made by bonding a layer of gold to a base metal, usually brass or copper. The gold layer must be at least 5% of the total weight of the item in order to be considered "gold-filled." This means that a gold-filled item is not solid gold, but rather a metal with a gold layer on the surface.
Gold-filled jewelry is more valuable than gold-plated jewelry because the gold layer is thicker and more durable. Gold-filled jewelry can last for many years with proper care and maintenance. However, it is important to note that gold-filled jewelry can still tarnish over time, especially if it is exposed to water, chemicals, or other harsh substances.