White Hat SEO is the generic term that refers to optimising any website without violating the terms of use (TOS) of all search engines which you need to use.
Search engines use small programs called robots to crawl and index the internet, this process is focused generally on making the site easier for a machine to understand at the same time to maintain a friendly interface for people.
White Hat search engine optimisation is different to Black Hat search engine optimisation. The title and meta tags in black hat SEO might be used in fooling most of the search engines by making search engines think that the page is about something which it is not – e.g. an entertainment website masquerading as an education site.
White Hat search engine optimisation is an honest and reliable approach when optimising your website and the common principle is to do your best in order to be liked by the major search engines like Google, Bing and Yahoo.
The whole strategy is to make a right coded website that makes it easy for search engines to understand and to mimic optionally about what should happen for web pages that are liked by users.
So, for example, if a guest found a site and found that it was a good site then he/she would possibly write a good article about it, create a topic about it on the different general forums or add it in his/her social sites, make a group for it and open the discussion so other people try it as well. White Hat accelerates this process and is sometimes an automated process.