The terms ‘white hat’ and ‘black hat’ come from the old black and white westerns where the hero always wore a white hat, and the bad guys always wore black hats. So obviously anyone who practices ‘White hat’ SEO is someone who abides by all the rules of the webmaster guidelines and who doesn’t try to use tricks or sneaky tactics to manipulate their search engine rankings. Good white hat SEO focuses on the content and accessibility of the website, making sure that the content is as rich and useful as possible, while at the same time, making it easy as possible for people to find and read the information on their website.
Interestingly, what Google decides as white hat or black hat is influenced by how much it trusts your website. An authoritative website with a high trust rank can get away with more than a fresh new website with few backlinks.