SEO is an acronym for “Search Engine Optimization“. The process of making a site “Search Engin Friendly” it’s called SEO. Search Engine Optimization refers to the collection of techniques and practices that allow a site to get more traffic from search engines (Google, Yahoo, Microsoft).
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.
SEO can be divided into two main areas: off-page SEO (work that takes place separate from the website) and on-page SEO (website changes to make your website rank better).
The First basic thing you need to know that Search engines are not humans. While this might be obvious for everybody, the differences between how humans and search engines view web pages. Unlike humans, search engines are text-driven. Search engines crawl the Web, looking at particular site items mainly text to get an idea what a site is about.
First, search engines crawl the Web to see what is there. This task is performed by a some 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.
After a page is crawled, the next step is to index its content in search engine. 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. 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 optimized your pages correctly and for you.
When a search request comes, the search engine processes it – i.e. it compares the search string in the search request with the indexed pages in the database. Since it is likely that more than one page (practically it is millions of pages) contains the search string, the search engine starts calculating the relevancy of each of the pages in its index with the search string.
There are various algorithms to calculate relevancy. Each of these algorithms has different relative weights for common factors like keyword density, links, or metatags. That is why different search engines give different search results pages for the same search string. What is more, it is a known fact that all major search engines, like Yahoo!, Google, Bing, etc. periodically change their algorithms and if you want to keep at the top, you also need to adapt your pages to the latest changes. This is one reason (the other is your competitors) to devote permanent efforts to SEO, if you’d like to be at the top.
The last step in search engines’ activity is retrieving the results. Basically, it is nothing more than simply displaying them in the browser.