Search Engine Marketing at the keyword level but optimize at the campaign level.
Search Engine Marketing, or SEM, is a form of Internet Marketing that seeks to promote websites by increasing their visibility in the Search Engine result pages (SERPs). According to the Search Engine Marketing Professionals Organization, SEM methods include: search engine optimization (or SEO), paid placement, and paid inclusion. Other sources, including the New York Times, define SEM as the practice of buying paid search listings with the goal of obtaining better free search listings.