Search Engine Marketing (SEM) is separated into two major areas: pay-per-click (PPC) search advertising and search engine optimization (SEO). The act of marketing a web site via search engines, whether this be improving rank in organic listings, purchasing paid listings or a combination of these and other search engine-related activities. A successful search engine marketing program will usually contain elements of both. SEM is an acronym for search engine marketing and may also be used to refer to a person or company that does search engine marketing.