What is the difference between gold filled and gold plated jewelry?

What is Gold Plated Jewelry?
A gold plated jewelry is comprised of a base metal (e.g. copper or brass) with a thin gold layer coated on the outside of the base metal, commonly with a nickle layer in between. Electroplating is typically used to process the nickel-plated base with gold plating. The amount of gold plated is usually 0.05% of the overall weight of the jewelry, so the gold plating can easily wears off quickly and subject to tarnish once the base metal is exposed. Therefore, gold plated jewelry should only be cleaned using a cotton ball if it's absolutely necessary. Never scrub a gold plated jewelry.
What is Gold Filled Jewelry?
A gold filled jewelry contains an actual gold layer of 10 karat or higher, that is pressure bonded to a base metal (e.g. silver, copper, brass) using pressure and heat. The amount of gold used is generally 5% (1/20) of the overall weight of the jewelry. Because of a thick gold layer, gold filled jewelry will rarely tarnish under good care. A gold filled jewelry should be cleaned with mild soap and water or untreated cloth.
How can I tell if my jewelry is gold plated or filled?
To determine if a jewelry is gold filled or plated without damaging the jewelry, we recommend first checking the metal stamp on the jewelry. Gold plated jewelry should be stamped with gold weight (e.g. 1/20). Alternatively, a jeweler can electronically test the jewelry's gold composition using a device.