Anyone who has ever been to a car show, boat show, or the home show has seen the kind of work promo models do. The answer seems obvious: the trade show models show the product. However, there is so much more to the job that it takes someone special to do it.
Trade show models indeed show the products. They are sent to an event with a promo staffing agency, working with a company that wants to increase product awareness and sales. They are promo models in the sense that they are working on a large scale of various products, and the client's product is one of those being shown.
Individual models generally work to promote a brand, as a brand ambassador. They dress in a way that calls attention to the general category of products. For example, an exercise equipment brand ambassador might dress in attractive workout clothing. A boat manufacturer's trade show models might dress in swimwear and life preservers.
The first thing the models do is to get the attention of the people who walk by at the convention or trade show. As a promo model, attractiveness is one way to accomplish this. However, in convention booths, it takes something extra. Convention models must engage the consumers in the presentation of the product. They do this by presenting themselves, being friendly, and talking to individuals about the product.