SEO may target different kinds of search, including image search, local search, video search, academic search, news search and industry-specific vertical search engines. This gives a website web presence.
Search engine optimization is the process of improving the visibility of a website or a web page in search engines via the "natural" or un-paid ("organic" or "algorithmic") search results.
Other forms of search engine marketing (SEM) target paid listings. In general, the earlier (or higher on the page), and more frequently a site appears in the search results list, the more visitors it will receive from the search engine's users. Read more about SEO