To understand SEO you need to be aware of the architecture of search engines. They all contain the following main components ·Spider ·Crawler ·Indexer ·Database ·Result engine ·Web server 1.Spider. This program downloads web pages just like a web browser. The difference is that a browser displays the information presented on each page (text, graphics, etc.) while a spider does not have any visual components and works directly with the underlying HTML code of the page. 2.Crawler This program finds all links on each page. Its task is to determine where the spider should go either by evaluating the links or according to a predefined list of addresses. 3.Indexer This component parses each page and analyzes the various elements, such as text, headers, structural or stylistic features, special HTML tags, etc. 4.Data base This is the storage area for the data that the search engine downloads and analyzes. Sometimes it is called the index of the search engine. 5.Result engine The results engine ranks pages. It determines which pages best match a user's query and in what order the pages should be listed. This is done according to the ranking algorithms of the search engine. It follows that page rank is a valuable and interesting property and any seo specialist is most interested in it when trying to improve his site search results. 6.Web server The search engine web server usually contains a HTML page with an input field where the user can specify the search query he or she is interested in. The web server is also responsible for displaying search results to the user in the form of an HTML page.
nice explanation How Search Engine works thanks pal for sharing!!! i also found a link how Google work please have a look
Actually search engines match queries against an index that they create. The index consists of the words in each document, plus pointers to their locations within the documents. This is called an inverted file. A search engine or IR system comprises four essential modules: 1. A document processor 2. A query processor 3. A search and matching function 4. A ranking capability Video on Demand Solutions