Search engine optimization is a methodology of strategies, techniques and tactics used to increase the amount of visitors to a website by obtaining a high-ranking placement in the search results page of a search engine (SERP) - including Google, Bing, Yahoo and other search engines.
It is common practice for Internet users to not click through pages and pages of search results, so where a site ranks in a search is essential for directing more traffic toward the site. The higher a website naturally ranks in organic results of a search, the greater the chance that that site will be visited by a user.
Conceptually, there are two ways of optimization:
On-Page SEO - It includes providing good content, good keywords selection, putting keywords on correct places, giving appropriate title to every page, etc.
Off-Page SEO - It includes link building, increasing link popularity by submitting open directories, search engines, link exchange, etc.