Search engine marketing, or SEM, is a type of Internet marketing that tries to promote websites by making them more visible in search engine result pages (SERPs). The Search Engine Marketing Professional Organization, recognizes SEM methods as: search engine optimization (or SEO), paid placement, contextual advertising, and paid inclusion. The New York Times among others defines SEM as the practice of buying listings from paid searches.

SEM Market structure

Search engine marketing is a huge business, generating massive amounts of capital. In 2006, search engine marketing spend by US advertisers was a colossal US$9.4 billion, a 62% increase compared to the year before and a massive 750% increase over the spend figure for 2002. The largest SEM vendors include the recognized ‘big three’, the most popular and regularly used search engines, Google AdWords, Yahoo! Search Marketing and Microsoft adCenter. Since 2006, SEM has been expanding greatly at a much faster rate than traditional and conventional advertising and even faster than expected to other channels that are the product of online marketing.