What is Search Engine Optimization or SEO?

from Wikipedia:
Search engine optimization (SEO) is a set of methods aimed at improving the ranking of a website in search engine listings. The term also refers to an industry of consultants that carry out optimization projects on behalf of clients' sites.

Using search engines, visitors can find sites in a variety of ways: via paid-for advertisements in the search engine results pages (SERPs), via third parties who are listed in the search engines, or via "organic" listings, i.e. the results the search engines present users. SEO is primarily about the latter.

High rankings in the organic SERPs usually translate into a lot of free, targeted traffic for the sites that rank well. Obtaining that traffic by other means can be expensive. For particularly competitive terms the cost of acquisition of a single visitor can be in excess of US$100. For even moderately competitive terms the cost can range from a few cents to several tens of dollars per visitor. Given those costs it often makes sense for site owners to optimize their sites for the free traffic search engines can send.

Not all sites have identical goals in mind when they optimize for search engines. Some sites are seeking any and all traffic, and may be optimized to rank highly for any commonly searched phrase. Other sites target a certain population, and are therefore concerned with their rank on specific search phrases that they believe that population will use. Sites may optimize to attract native speakers of a particular language, to attract visitors from a specific geographical location, or even to attract visitors who use certain misspelling of the target keyword.

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