That means buying and selling, and the manufacture of goods to buy and sell. Anything that makes money, really, as opposed to nonprofit and not-for-profit businesses (churches, charities, social organizations, etc.).
Unless you mean commercial advertising spots? Americans call them commercials, Brits call them adverts, but they are radio and television spots advertising a (commercial) product. Those in the 'commercial industry' could be likened to those in the 'film industry' but on a smaller scale, for that definition.