Commodities is a term specifically used for an economic good or service when the demand for it has no qualitative differentiation across a market. Examples include wheat, petroleum, salt, gold, copper, rice, and others whose supply and demand are a part of one universal market.
Soft commodities are goods that are grown, while hard commodities are ones that are extracted through mining. Another important class is energy commodities which includes electricity, gas, coal and oil.
vCalc's Commodities library contains mathematical content cutting across various commodities.