Introduction
What is a Search Engine?
Search engines are the primary tools of Internet users for finding products, services and information over the web. Search engines allow people to search the entire Web (or at least those pages of the Internet that are in the search engine's database.)
How Does a Search Engine Index Web Pages?
There are four parts to an engine that you need to know about for optimization purposes:
There are two ways that your site can get into the database:
What Happens When I Submit my URL to a Search Engine?
First, the search engine's spider visits your URL immediately and schedules your page for inclusion in the search engine's database.
Second, usually within a few weeks, the spider comes along and places your page(s) into its database. There is no telling how many pages deep the spider will crawl or how many pages it will place in the database. Usually, on the first time around, it will be only a few pages -possibly only the home page.
Third, the spider revisits your page(s) to grab any changes you've made. (The old term for this was "automatic update.") Once a page is in the database, the spider usually revisits every few weeks. The spider will also begin to crawl your site more deeply and place more and more of your pages into the database.
Fourth, when people use a search engine, they type keywords into a search box on the search engine's website. They are submitting a query. The search engine, depending on algorithms, will pull up all of the sites relevant to that query.
What is the Difference between a Search Engine and a Directory?
A search engine is a machine - or a robot. A human may program algorithms for a search engine, but humans have nothing to do with your site when the spider is visiting your site or when the engine is ranking your pages. Google.com is an example of a search engine.
For the most part, humans compile directories. Dmoz.org (Open Directory Project) is an example of a directory. When you submit your site to Dmoz, a human will review your site for consideration in the Dmoz directory of web sites.
A search engine has a very large database because it will store several pages of every web site it indexes. A directory will only store a link to the home page of each site and a description.
Search engines will take the description either from some of the sentences on the web page or from the description meta tag. A directory will take the description from your submission information.
Each major search engine is usually associated with a directory. For instance, when you go to Google and you type in a search, you are getting results from all the web sites stored in Google's database. It is believed that Google's algorithms are also programmed to place emphasis on sites that are also listed in the Dmoz directory. However many top SEO’s argue this holds less weight today.
It is a good idea to get listed in as many directories as possible. This simple piece of software can save you a lot of time