Search Engine Optimization (SEO) is the process of improving the amount of traffic to a website and/or improving the quality of traffic to a website (or specific web pages) which comes from search engines via “natural” (i.e., un-paid, “organic” or “algorithmic”) search results – this does not also include, and is many times confused with also including, other forms of Search Engine Marketing (SEM).
The activity of SEM usually means paid inclusions into search engines, directories or other placements on other sites of a paid nature, and this is not SEO, but can boost the effectiveness of SEO activities.
The theory behind SEO is that the higher to the top of a search engine results page your link appears, the more visitors your site will receive from the various search engine users.
SEO may target different kinds of search, including local search, video search, image search and/or industry-specific vertical search engines. Also as an Internet marketing tactic, SEO considers what people search for and how search engines work.
SEO involves what is called on-page and off-page methods.
The optimization of a website for on-page primarily involves editing the sites content (i.e., HTML outputs) and associated META coding to both increase the sites relevance to specific keywords or phrases and to remove barriers to the indexing behavior of search engines.
Off-page SEO involves performing actives that are not of a paid-for nature on other sites, such as posting to forums, in the hopes of making a site seem more relevant to the search engines.