In macroeconomics, a industry is part of an overall economic system that produces a closely related group of products, raw materials, or service. For instance, one could refer to the metal industry or to the textile industry. In the micro-emergent world of micro finance, the banking industry would be considered a micro-industry within an overall micro-industry of lenders and products. The definition of what an industry is depends on who you ask for the definition.
For most people in the United States, the most common definition of what an industry is any activity involving production of material goods that are sold for revenue in order to make a profit. In most modern economic discussions, however, the definition of what an industry is largely precludes any large scale production of goods for sale to customers. Instead, what many economists define as an industry is the buying and selling of small scale, repetitive, and process oriented activities that are necessary for the production of large scale, often complex, products such as machinery or construction equipment. The definition of what an industry consists of is thus very different than the standard view of what a business or company is.
For example, most people would likely consider automobile manufacturing to be a production of intermediate goods that are necessary for the production of a new vehicle. On the other hand, if we look at the definition of an industrial unit of labor as being anything from 20th century tractors to assembly lines, then we are potentially defining an industry including mining, agricultural, and industrial activities. While the traditional definition of what an industry includes is manufacturing and the processing of finished goods, the definition is much more flexible. Therefore, it is not surprising that mining and petroleum exploration are included within the scope of the term industry.