Search Engine Marketing (SEM) consists of different techniques to connect a search engine's technology. SEM include SEO and PPC (Pay-Per-Click) ads. SEO and SEM are often used interchangeably. But, SEO is a subset of SEM. The question here arises that what is the difference between SEO and SEM. SEO's aim is to provide organic search results for free while with SEM, search are not always be free as it uses paid ads for the certain keywords on search engine results page. Read more at: http://www.socialmediatoday.com/content/what-main-difference-between-seo-and-sem