Black hat SEO refers to techniques and strategies used to get higher search rankings, and breaking search engine rules. Black hat SEO focuses on only search engines and not so much a human audience. Black hat SEO is typically used by those who are looking for a quick return on their site, rather than a long-term investment on their site. Some techniques used in black hat SEO include: keyword stuffing, link farming, hidden texts and links, and blog content spamming. Consequences of black hat SEO can possibly result in your site being banned from a search engine and de-indexed as a penalization for using unethical techniques.
White hat SEO refers to the use of techniques and strategies that target a human audience opposed to a search engine. Techniques that are typically used in white hat SEO include using keywords, and keyword analysis, doing research, rewriting meta tags in order for them to be more relevant, backlinking, link building as well as writing content for human readers. Those who use white hat SEO expect to make a long-term investment on their website, as the results last a long time.