What is Gold filled

Gold filled
Gold-filled jewelry is composed of a solid layer of gold (requires at least 1/20th or 5% of its weight) bonded to a base of some metals. Gold filled jewelry is more tarnish/discolor resistant than gold plated jewelry (vermeil and regular), and with good care they are great for daily wear and last for years. 
High quality, hypoallergenic, second best to solid gold and is more affordable.