Arbitrage refers to the virtually-simultaneous purchase and re-sale of a product for the purpose of locking in a risk-free profit.
Gold and Silver are two of the most popular and widely traded commodities owing to their high liquidity. Precious metals arbitrage involves buying and selling quickly to benefit from the difference between the buy and sell price ('bid' and 'ask' price). For example, the gold price on one marketplace may be a few pounds, dollars or euros lower than on another. Traders buy at the low price and immediately sell at the higher price to make a profit.