Search Engine Marketing, or SEM, is a form of Internet Marketing that seeks to promote websites by increasing their visibility in the Search Engine results pages (SERPs) and has a proven ROI (Return on Investment). 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, different from SEO which seeks to obtain better free search listings.

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