Search Engine Marketing (SEM) is about building and maintaining your website's visibility within the search engines through the use of natural organic optimization techniques as well as paid search (or sponsored listing) campaigns. Search engine optimization (SEO) is the process of affecting the visibility of a website or a web page in a search engine's "natural" or un-paid ("organic") search results. In general, the earlier (or higher ranked on the search results page), and more frequently a site appears in the search results list, the more visitors it will receive from the search engine's users. SEO may target different kinds of search, including image, local, video, academic, news and industry-specific vertical search engines.