SEO is based on the relevance of your content in relation to the used keywords. Spiders crawl through the internet to index millions of sites on a regular basis. These spiders crawl through your entire website looking for keywords, the quality of incoming links, originality of your content.
If you link to sites with a high Page rank, it will improve your rank in the search results. The search engine spiders browse through your content and follow all the links on your site, similar to how a human goes through your website. Since these spiders can only crawl through content (letters, words, sentences) it is irrelevant to put videos, pictures, music on your website because the spiders cannot see what this content is about.
The key principle of SEO says “original content is King”. If you duplicate or copy paste content, Google will devalue your website.
A good balance between incoming and outgoing links is also from initial importance. If a lot of websites with a low page rank link to your site, you will get a lower rank in the search results.
Search Engine Optimisation is sometimes also called SEO copyrighting because most of the techniques that are used to promote sites in search engines deal with text. Generally, SEO can be defined as the activity of optimizing web pages or whole sites in order to make them more search engine-friendly, thus getting higher positions in search results.
SEO activity does not automatically guarantee you top ratings but if you neglect basic rules, the results are bound to suffer. Also, if you set realistic goals – i.e. to get into the top 30 results in Google for a particular keyword, rather than be the number one for 10 keywords in 3 search engines, you will feel happier and more satisfied with your results.