What Is A Search Engine?

To those new to the Internet, the first question they might ask is, "What is a search engine?" Search engines are computer programs that scour the internet and gather information about websites. The information they gather is placed in an indexed reference for those pages into a massive database.

1. Search engines continuously scan the internet to add to their databases. At the same time, they check previously scanned sites and update information already in their databases.
2. Web crawlers, spiders, robots, bots and automatic indexers are names that refer to search engines. The most well-known search engines are Google, Yahoo and Bing, but there are many others including Alexa, InfoUSA, Netscape, AOL, AllTheWeb, AltaVista, Go.com, Ask, Teoma, HotBot, Excite, Lycos, Searchit and Gigablast.
3. Keywords and phrases are at the heart of search engine design. A search engine user submits a word or phrase based on the information he is looking for. It’s the job of the search engine to determine which webpages contain the information that is being sought.
4. With billions of pages of information on the internet, search engines not only need to locate the webpages that contain the information the user is seeking, but also present the list of pages in an order of most likely to be useful. Complex formulas for determining the rank of a webpage in relation to specific keywords and phrases have been developed. One of the most sophisticated ranking systems is utilized by Google, called PageRank(TM). A page with a higher PageRank is considered to be more important or more relevant to the search term, and thus will be placed ahead of a webpage that has a lower rank value. This benefits the person who is using the search engine, as ideally the most relevant sites will appear first on the list.
5. The term "search engine optimization" (SEO) refers to the process of structuring a webpage to ensure a listing with various search engines and to be placed high on their list when relevant keywords are searched. There are many factors used in designing webpages to address search engine optimization. One factor is the number of times a keyword or phrase appears naturally on the page ("keyword density"). Google considers the position of search terms within a page and the proximity of those search terms to one another on the page as a factor in determining a site’s ranking. Some search engines give extra weight to keywords found at the top of a page as opposed to the bottom. This is referred to as placing items "above the fold," which is a term borrowed from the newspaper industry. "Above the fold" refers to everything on a newspaper page that can be seen without the reader flipping it over to see the rest of the page. Similarly, placing the most important items on a webpage on the top part of the page so that they can be seen without requiring the user to scroll down is a popular SEO technique.
6. Search engines find and index every page, but this takes time. When a new website is created, the owner will often register his site with some of the search engines which allow for site registration. While search engines should eventually discover their site, this can speed up the process of being included in a search engine's database.

References:

The Anatomy of a Search Engine