There are two main types of real search engine optimisation (not including Paid Search Results) - Organic and Artificial. Part of the search engines objectives is to recognise the artificial one and discount it, but what are they?
Well when a website is launched, if it contains good content, other people will link to it. They might place links on their own websites or via social networks such as Facebook and Twitter. This is organic because it is happening naturally and it can happen in hours or over years.
Fast organic growth is possible when a website "goes viral". It so impresses individuals that they tweet about it and those receivers tweet it on, or it appears in the press and on television, or large numbers of webmasters add links to it, or any mixture of the above.
The Facebook page Physics doesn't exist, it's all gnomes so caught the imagination of internet users that over 80,000 people became fans and over 5,000 websites added links to it. It was mentioned in the national media (off line and on line) further reinforcing it's popularity.
This is true organic search engine optimisation and it can be recognised by the major search engines because the links appear in a wide variety of contexts with different text. For example one site might link to it with the text "this is a great site" while another uses "I told you there was no physics".
A good SEO company will try to mimic this although it is time and resource intensive work as every link of mention must be fairly unique. They may, for example, spend some time in a forum discussing a point before finally adding a link to the site they are optimising just as a normal individual would. This done they will have created what appears to be an organic link and it will carry a great deal of weight with the search engines.
Bad, or should we say cheaper, SEO companies use artificial optimisation where they concentrate on quantity, rather than quality. This can work in the short term until the search engines start to recognise that the links have a pattern (they are the same or nearly the same or appear in very similar contexts) at which time they will discount them.
Artificial optimisation, therefore, allows a SEO company to show results (and get paid) even though they may be temporary.
For more information on effective link building see our page Links in SEO.
I'm Tim Hill, a Search Engine Optimisation and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.