What is a search engine?
A program that searches documents for specified keywords and returns a list of the documents where the keywords were found. Although search engine is really a general class of programs, the term is often used to specifically describe systems like Google and Yahoo that enable users to search for documents on the World Wide Web and USENET newsgroups. Typically, a search engine works by sending out a spider to fetch as many documents as possible.
Another program, called an indexer, then reads these documents and creates an index based on the words contained in each document. Each search engine uses a proprietary algorithm to create its indices such that, ideally, only meaningful results are returned for each query.
What is Search Engine Optimization?
Search Engine Optimization, also known as SEO, is the process of increasing the amount of visitors to a Web site by ranking high in the search results of a search engine. The higher a Web site ranks in the results of a search, the greater the chance that that site will be visited by a user. It is common practice for Internet users to not click through pages and pages of search results, so where a site ranks in a search is essential for directing more traffic toward the site. SEO helps to ensure that a site is accessible to a search engine and improves the chances that the site will be found by the search engine.
Some commentators, and even some SEOs, break down methods used by practitioners into categories such as "white hat SEO" (methods generally approved by search engines, such as building content and improving site quality), or "black hat SEO" (tricks such as cloaking and spam indexing).
White hatters charge that black hat methods are an attempt to manipulate search rankings unfairly. Black hatters counter that all SEO is an attempt to manipulate rankings, and that the particular methods one uses to rank well are irrelevant.
The Relationship between SEO and The Search Engines:
The first mentions of Search Engine Optimization don't appear on Usenet until 1997, a few years after the launch of the first Internet search engines. The operators of search engines recognized quickly that some people from the webmaster community were making efforts to rank well in their search engines, and even manipulating the page rankings in search results. In some early search engines, such as Info seek, ranking first was as easy as grabbing the source code of the top-ranked page, placing it on your website, and submitting a URL to instantly index and rank that page.
Due to the high value and targeting of search results, there is potential for an adversarial relationship between search engines and SEOs. In 2005, an annual conference named Air Web was created to discuss bridging the gap and minimizing the sometimes damaging effects of aggressive web content providers.
Some SEO companies employ aggressive techniques that get their client websites banned from the search results. The Wall Street Journal profiled a company which allegedly used high risk techniques and failed to disclose those risks to its clients. Wired reported the same company sued a blogger for mentioning that they were banned. Google's Matt Cutts later that Google did in fact ban Traffic Power and some of its clients