Well, that is rather complicated to explain in detail, but I will try to summarize!
White hat SEO is the way by which you optimize using all the SEO tactics considered ETHICAL and honest in order to achieve good SERPS. It often takes a lot of time and can be time consuming. But results will help give your site prestige in addition to great placement.
Black hat SEO is the process by which you achieve SERPS placement using tactics that are completely unethical. The results are immediate but will not last. When you are caught implementing black hat SEO you can face severe consequences like site banning.
Grey hat is just the combination of both white hat and black hat SEO tactics.
Ultimately, if you really care about your site and are serious about online success, stay away from any shade that is NOT White Hat SEO.
Basically it all has to do with whether you're doing something that is considered a good practice to make your site more user friendly, versus doing something to try to game the search engines to artificially increase your ranking by exploiting a problem with the current algorithm. This might be a huge benefit, but only be temporary until the search engines plug the exploit, at which time they may decide to go ahead and ban any site that was taking advantage.
Black Hat - adopts unethical or illegal ways which are not acceptable by search engine. Its results are fsat but temporary.
White Hat- adopts legal techniques. Though its result is slow but permanent.
Grey Hat- it is the combination of the black and white hat. Its not completely safe and not completely dangerous.
white hats eo practice include building traffic and backlinks using orgainc seo..
while black white include illegal techinuques like paid traffic or backlinks which no doubt help the website but for a short term..so black hat and gray hat seo is not recommended
Black hat and white hat seo , the difference between these terms can simply be define that , if you obey the guidlines of the search engines for site optimizing than you are doing the white hat and if you are doing SEO according to the guidelines than you are doing black hat seo and if you are mixcing these these rules some you are following and some do not than you are doing gray hat SEO .