Fit out the stage for theater productions.
The defining characteristic of a Commercial Photographer is that your work is purchased as images rather than art. You produce products that have utility—they help sell a product or set a scene.
“Commercial” refers to a subset of Photographers rather than a specific field. For example Advertising Photographers, Fashion Photographers, and Portrait Photographers could all be referred to as Commercial Photographers because each of those fields are paid to produce images for a commercial purpose. Whereas Fine Art Photographers, for example, fall outside of this field.
As a Commercial Photographer, you combine the standard techniques of any photographic field—artistic vision, an eye for angles, competency with your technical equipment, and proficiency in staging shots—with the business acumen to contract and communicate with clients. You are photographing your subjects for a purpose, and you need to understand what that is and work it into your shoot.
For example, if you are shooting a fashion spread for a jeans company, your job is both to make the photograph look beautiful and to give the jeans a center prominence in the picture. So at this position you are paid to incorporate commercial interests into your artistic design.