[header] How to buy commodities [title] Familiarize yourself with the concept of commodities. [step] A commodity is simply a good that is interchangeable with other commodities of the same type, and that is usually produced and sold by many different companies. For example, a barrel of oil of one particular type, such as brent crude, is the same product regardless of who makes it. 
[substeps] This is opposed to a consumer product like a computer or automobile, for example. These products differ dramatically between producers and cannot be easily exchanged for one another.