A commodity in economics is a good, such as food, metals or grains, which is interchangeable with similar goods, and which is available in large quantities.
Investors can buy or sell on commodities exchanges using futures contracts.
More generally, a commodity is any good in a competitive market.
In general parlance, a commodity is a good where the good supplied is indistinguishable from one supplier to another. A consumer, then, only considers price when making a purchasing decision. In recent years, computers have become a commodity.