SEO is a technique which helps search engines find and rank your site higher than the millions of other sites in response to a search query. SEO thus helps you get traffic from search engines.
How Search Engines Work
The first basic truth you need to know to learn SEO is that search engines are not humans. While this might be obvious for everybody, the differences between how humans and search engines view web pages aren’t. Unlike humans, search engines are text-driven. Search engines are far from intelligent creatures that can feel the beauty of a cool design or enjoy the sounds and movement in movies. Instead, search engines crawl the Web, looking at particular site items (mainly text) to get an idea what a site is about. This brief explanation is not the most precise because as we will see next.
First, search engines crawl the Web to see what is there. This task is performed by a piece of software, called a crawler or a spider. Spiders follow links from one page to another and index everything they find on their way. Having in mind the number of pages on the Web, it is impossible for a spider to visit a site daily just to see if a new page has appeared or if an existing page has been modified, sometimes crawlers may not end up visiting your site for a month or two.
What you can do is to check what a crawler sees from your site. As already mentioned, crawlers are not humans and they do not see images, Flash movies, JavaScript, frames, password-protected pages and directories, so if you have tons of these on your site, you’d better run the Spider Simulator see if these goodies are viewable by the spider. If they are not viewable, they will not be spidered, not indexed, not processed, they will be non-existent for search engines
After a page is crawled, the next step is to index its content. The indexed page is stored in a giant database, from where it can later be retrieved. Essentially, the process of indexing is identifying the words and expressions that best describe the page and assigning the page to particular keywords. For a human it will not be possible to process such amounts of information but generally search engines deal just fine with this task. Sometimes they might not get the meaning of a page right but if you help them by optimizing it, it will be easier for them to classify your pages correctly and for you – to get higher rankings.
The last step in search engines’ activity is retrieving the results. Basically, it is nothing more than simply displaying them in the browser