1. White Hat SEO  

White hat SEO is one of the most popular SEO techniques and it utilizes techniques and methods to improve the search engine rankings of a website which do not run incorrectly of search engine guidelines. The white hat SEO techniques include Proper use of a title, keywords, and meta tags, high-quality content development, site performance, link acquisition campaigns which supported by high-quality content. If we choose this type of SEO technique then we can expect a gradual, steady but lasting growth in ranking. 

2. Black Hat SEO 

Black Hat SEO is a type of SEO techniques that try to trick the search engine and manipulate the ranking of the site. This type of method of SEO is not in accordance with the SEO guidelines set by search engines and especially Google. The wholesome level of SEO technique is very low because of some technique of black hat SEO include keyword stuffing, doorway and cloaking, link spam, hidden link, and hidden text. In this technique you can expect unpredictable, quick and short lasting growth in rankings. 

3. Grey Hat SEO 

Grey Hat SEO is not white and not black but gray, is midway between of both black and white SEO it's basically all about the balance between risk and reward.