White Hat SEO is optimizing your web pages in an ethical way so that they rank better in the search engines.
Black Hat SEO is using tricky and unethical practices to try and get higher rankings.
The search engine understandably does not like Black Hat techniques. You may wonder what these composer of.
Here are some Black Hat techniques that you should avoid if you value your rankings:
Cloaking: This is a technique that displays different content to the search engine and the visitors. This way they can add many keywords to what the search engines see. This may be unreadable to humans. Then the humans are fed another page design for them.
Duplicate Content: Some sites will use duplicated content which is frankly spammed. This could be duplicate content on the same site or content that was copied from another site. If you abuse this technique than you could be banned from some search engines.
Irrelevant keywords: in the meta tags If you add keywords in the Meta tags that are not actually on the web page, then this is considered spamming. If you want your rankings lowered then that's the way to do it.
Linking to Bad Neighborhoods: Make sure you only link to Good Neighborhoods. Do not link to sites that spam or use any type of Black Hat SEO. That will certainly backfire on you.
Hidden Text: If you try to add hidden text by making the text color the same as, or close to the background, then that's Black Hat SEO and you could very easily be removed from the search engines. This also goes for very tiny text. If your visitors can not read it easily, then it better not be there!
More than one Title: Just like keyword stuffing, do not do it. You should only have one title tag per page. Be careful, sometimes you can do this accidentally. Double check to make sure there's only one title tag.
Sometimes Black Hat can deliver fast results, but they do not last long. Sometimes your rankings will drop way down or you could be banned from the search engines.
You can get great, long-lasting results from White Hat SEO. So do not fool with the latter.
SEO is not spam unless you abuse it. Just use common sense. Write good content with your visitors in mind. Do not try to trick them or the search engines.
White Hat SEO evolves writing good quality content. Do not try to use spammy tricks. Deliver great content to your visitors and the search engines. Do not hide text, or stuff Meta tags with keywords that should not be there. Make sure your title tag and other Meta tags reflect your page.
Just do not do anything that you feel uncomfortable about. Double check your content and Meta tags for errors. Use only White Hat SEO techniques that are lasting and honorable.
Using White Hat SEO will take you to the top of the rankings, while the Black Hat abusers will eventually fall right off the web.