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Gold is a chemical element (symbol Au, atomic number 79). It is not chemically reactive, and is found in elemental form as nuggets or grains in rocks and rivers that eroded them. Its apparent indestructibility, brightness, and color have made it very desirable throughout recorded history. It was used as a basis for currency for a really long time. Due to its high malleability, ductility, resistance to corrosion, and electrical conductivity it also has multiple industrial, medical, and culinary applications. The world consumption of new gold produced is estimated to be about 50% in jewelry, 40% in investments, and 10% in industry. 
Gold is occasionally used as a food additive, with the E number E175, and is also known as aurum and "Pigment metal 3". There is a lack of evidence as to its safety or danger in food. As a food additive, it is mainly used for decoration, either as gold leaf or in small particles as powder. There is no firm evidence on the safety of eating gold, but because of its low solubility it is unlikely to have much effect on the human body (except in a few people who exhibit an intolerance to gold). Gold nanoparticles can be absorbed by the body, and if absorbed it can be found in serum, breast milk, and urine, but particles used in food are normally large enough to minimise risk of absorption.
Compounds of gold, particularly gold (I), have been used in medicine including to treat tuberculosis and arthritis. Preparations such as Auranofin and gold thiolates are used to treat rheumatoid arthritis.
Gold in collodial or monatomic formulation is sometimes sold as an alternative medicine. According to the website Monatomic Orme, "Monatomic Gold is a powerful electrical conductor that has been known to help with physical and mental energy." However, energy in the body is not transported as electricity but in chemical form. So it really isn't clear how it could work.
- Scientific Opinion on the re-evaluation of gold (E 175) as a food additive, European Food Safety Authority, EFSA Journal 2016;14(1):4362, Wiley
- See the Wikipedia article on Auranofin.
- Monatomic Gold, Monatomic Orme, accessed 7 Jan 2019