Sales marketing jobs involve the promotion and selling of products, brands, or services. Careers in these sectors usually concentrate on specific aspects of the advertising and selling process. As a market research professional, your responsibilities are to define target demographics and collect data that helps marketing managers and marketing specialists create a strategy and design a campaign to promote a product or service. The duties of sales representatives involve selling the products or services to businesses, retailers, or end users. Sales professionals often have a goal or a sales quota for each week or month, so you must ensure that you are productive and reaching as many prospective clients as possible.