From the same link.
"This form of marketing touches fewer consumers for the cost than traditional advertising media, but the consumer's perception of a brand, product, service, or company, is often more affected by a live person-to-person experience. While each model may not be directly employed by the company they represent, they can be trained to answer questions and provide customer feedback regarding products, services, and brand appeal. The responsibilities of the promotional model depend on the particular marketing campaign being carried out, and may include: increasing product awareness; providing product information; creating an association in the consumer's mind between the product or brand and a particular idea; handing items to consumers, such as a sample of the product itself, a small gift, or printed information. Marketing campaigns that make use of promotional models may take place in retail stores or shopping malls, at trade shows, special promotional events, clubs, or even at outdoor public spaces. They are often planned at high traffic locations to reach as many consumers as possible, or at venues at which a particular type of target consumer is expected to be present."