Search Engine Optimization is the process of improving the visibility of a website on organic (“natural” or un-paid) search engine result pages (SERPs), by incorporating search engine friendly elements into a website. A successful search engine optimization campaign will have, as part of the improvements, carefully select, relevant, keywords which the on-page optimization will be designed to make prominent for search engine algorithms. Search engine optimization is broken down into two basic areas: on-page, and off-page optimization. On-page optimization refers to website elements which comprise a web page, such as HTML code, textual content, and images. Off-page optimization refers, predominantly, to backlinks (links pointing to the site which is being optimized, from other relevant websites).
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. Although technology advances rapidly, 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, search engines perform several activities in order to deliver search results – crawling, indexing, processing, calculating relevancy, and retrieving.
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 (or Googlebot, as is the case with Google). 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 (over 20 billion), 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.