Search engine marketing (SEM) is a method used by owners of websites to enhance their presence on a search engines. Quite literally, it is marketing your website over a search engine and its aim is to promote websites by increasing their visibility in search engine result pages (SERPs).
Where search engine marketing is a way for website owners to increase their site’s visibility on a search engine, it is a primary revenue source of search engines. Search engine marketing involves many methods. It encompasses search engine optimization (SEO), paid placement, paid inclusion and contextual advertising. Out of the 4, search engine optimization does not yield revenues for the search engine, whereas the other 3 do.