Search engine optimization is a methodology of strategies, techniques, and tactics used to increase the number 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.
There are two kinds of SEO
1. On page Optimization
2. Off Page Optimization
In search engine optimization, on-page optimization refers to factors that have an effect on your Web site or Web page listing in natural search results. These factors are controlled by you or by coding on your page. Examples of on-page optimization include actual HTML code, meta tags, keyword placement and keyword density.
Off page, optimization refers to techniques that can be used to improve the position of a website in the search engine results page. The best SEO techniques for off page are social bookmarking, Forums, PPT / PDF Creation // Submissions, Image /Infographics Creation and Submission, Guest Posting, Social Signals, Microblogging and Blog Commenting.