Two broad categories in which SEO can be divided are...

White Hat SEO and Black Hat SEO are the main two categories in which SEO can be broadly divided into.

White Hat SEO

White Hat SEO refers to the usage of SEO strategies, techniques and tactics that focus on creating contents for human users, not for search engines. It completely follows search engine rules and policies. Some examples of White Hat SEO techniques are: using keywords and keyword analysis, backlinking, link building to improve link popularity. White Hat Strategies Relevant content Well-labeled images Relevant links and references Complete sentences with good spelling and grammer. Standards-compliant HTML Unique and relevant page titles

Black Hat SEO

Black Hat SEO refers to the usage of aggressive SEO strategies, techniques and tactics that focus only on search engines and not a human user. It usually does not comply with the search engines rules and policies. Some examples of Black Hat SEO techniques are: keyword stuffing, invisible text and doorway pages. Black Hat Strategies Duplicate Content Invisible text and stuffed keywords Cloaking or re-directing the user to another site or page Links from sites with non-relevant keywords