Black Hat: The use of methods such as link farms, keyword stuffing, cloaking, and article spinning that degrade both the relevance of search results and the user-experience of search engines. Basically, anything tactic that could be seen as unethical. White Hat: Quality content creation, easy navigation, clean code, high quality relevant inbound links, unsolicited inbound links. Pretty much anything that will make for a good user experience. The goal is to make your site for your user, not for the search engines.
what hat- search engines love it and it doesn't pollute the internet.. black hat- keywords stuffing, link farming, Hidden Links and etc..
White Hat Techniques - Getting increasingly difficult for webmasters Black Hat Techniques - Getting increasingly difficult for search engines to understand
black hat is unethical use of keywords and stealing content. White hat is optimizing with a good conscience...