What are the different types of SEO

Basically, (Organic, natural or un-paid SEO) SEO is divided into two main categories. These are On page Optimization and off page Optimization.

On Page Optimization: On page optimization is the optimization techniques which are used on the page of the website. All the changes are on the page of the website and all are visible on the website.

Off Page Optimization: Off Page Optimization is the optimization techniques which are used everywhere except on the pages of the website. This optimization does not deal visibly on the website pages. Basically links are generated by using this technique. Some of the off page optimization techniques are :
Link Building ,Article Submission,Social Bookmarking,Press Release,Blog Comment,Directory Submission

Social Media Marketing (Hangouts, Facebook, Twitter, Myspace and so on )

In brief, through SEO we get connected with other websites of same relevancy and also keep,changing our website’s content and structure as per Google strategies. And in result, we get huge,traffic to our website, increase the ranking of our website in various search engines and also increase,visibility.
Links allow the search engines’ ‘crawler’ or ‘spider’ (which is an automated robot) to find billions of interlinked documents on the web and then it links them with the search users’ query. As soon as the crawler finds these pages, they translate the websites’ code and then applies that on to a massive database. To manage holding all the pages that are accessible in milliseconds, the search engine companies have constructed data-centres all over the world.

There are basically three types of search engines:

Those that are powered by robots (called crawlers; ants or  spiders)
Those that are powered by human submissions
Those that are a hybrid of the two.

These storage holders have a very fast since they need to give accurate search results almost instantaneously, or put up with dissatisfied users. Popularity and relevance aren’t determined manually. Instead, the engines employ mathematical equations (algorithms) to sort them in relevance, and then to rank the relevance in order of quality (popularity). When search engines started, websites with keywords that linked to the users search came up, it was a very simplistic step and could often lead to a dissatisfied user. Whereas, now smart engineers have developed hundreds of factors that influence relevance and the results displayed, such as location.
How people use search engines has definitely changed since 1990, but the primary aim is still to conduct a search on your query.

Read More on search engine optimization