It is the technique which is used to enhance the traffic to a specific web site on being searched from a search engine. Search engines arrange the search result of web sites in accordance to relevance. The higher a site ranks in the search results, greater traffic it attracts. To flourish in the market companies have to get the right kind of traffic in large volume directed to their sites. It has been seen that searchers search the search result pages from top to bottom and form right to left. Hence having a position near the top is beneficial to the web sites.

Companies are spending a large amount of resources after SEO to get their sites indexed with a higher rank by the search engine robots when competing with the large number of sites of other companies whose sites are also among the search results for the same phrase. A lot of work is involved and a large amount of information is required to be maintained for doing SEO. What are phrases that people use maximum for searches, what is algorithm of the search engines, how do the search engine robots spider the results and many other technical intricacies are required to be considered during SEO. SEO projects often include web designing, modification of web sites, providing some unique contents that enhance the rank of the search engine results and maintaining and upgrading a lot of information for the technicalities. Usually SEO projects are done as a part of larger projects.

Content providers and webmasters started optimizing search results from the mid 1990s. They started understanding the value of the rank of the sites in a search result. Within the year 1997 the competition started becoming and aggressive and some webmasters were found to manipulate the rank of their websites in search results. Search engines started adjusting their techniques to prevent the web sites to get a manipulated rank in their search result. With the growing competition and high probability of SEOs and search engines, an annual conference in 2005 named, AIRWeb, Adversarial Information Retrieval on the Web, was created for discussing and minimizing the harmful effects of aggressive manipulation of search results by web masters and content providers.

Huge traffic doesn't always mean greater sale, hence SEO might not be the best marketing strategy for all web sites. There are other issues other than simple organic search algorithms of the search which tend to change periodically, such as paid advertisements, providing sponsored links on search engines and on other web sites. These prevent the web sites from being crawled by the search engines. It has been seen in recent times that unlike SEO providing sponsored links on other popular web sites bring more sales. Web sites that depend on online traffic often suffer from following SEO if the search engine in question changes heir algorithm and stops providing enough traffic.