Search engine optimization (SEO) is the art and science of getting pages to rank higher in search engines such as Google. Because search is one of the main ways in which people discover content online, ranking higher in search engines can lead to an increase in traffic to a website.
In Google and other search engines, the results page often features paid ads at the top of the page, followed by the regular results or what search marketers call the "organic search results". Traffic that comes via SEO is often referred to as "organic search traffic" to differentiate it from traffic that comes through paid search. Paid search is often referred to as search engine marketing (SEM) or pay-per-click (PPC).
Search engine optimization is a key part of online marketing because search is one of the primary ways that users navigate the web.
Search results are presented in an ordered list, and the higher up on that list a site can get, the more traffic the site will tend to receive. For example, for a typical search query, the number one result will receive 40-60% of the total traffic for that query, with the number two and three results receiving significantly less traffic. Only 2-3% of searchers click beyond the first page of search results. Thus, even a small improvement in search engine rankings can result in a website receiving more traffic and potentially business.
Because of this, many businesses and website owners will try to manipulate the search results so that their site shows up higher on the search results page (SERP) than their competitors. This is where SEO comes in.