What is White Hat SEO?
White Hat SEO refers that work within search engines terms of service to improve a site’s Search Engine Results Page (SERP) rankings while maintaining the integrity of your website and staying within the search engines’ terms of service.

White hat SEO is a set of by-the-book, ethical, technical, and aesthetic practices that an individual or group of individuals employ in the attempt to improve search engine results for a website or group of websites. White hat SEO describes the bulk of SEO best practices by reputable companies.

Advantages of White Hat SEO :

Security : As opposed to its black hat, White hat SEO techniques are not penalized by Google, as they abide by Google’s guidelines and rules.

Ethical : If you manage to get in the top positions with white hat SEO, it will be because you are doing things right and bringing real value to the users.

Stability : Pages that use black hat techniques may manage to position quite quickly, but when they are caught and penalized they drop in the rankings just as quickly. Instead, optimizing pages using white hat methods ensures that your position stays more stable, even if there are changes in Google's algorithms.

Profitability : White hat techniques manage to generate high quality organic traffic, which in turn results in an increase in all digital marketing indicators (lead generation, conversions, etc.). This means that by using white hat SEO methods, your traffic quality will also be higher as the traffic is likely more qualified.
What is Black Hat SEO?
Black hat SEO refers to a set of practices that are used to increases a site or page’s rank in search engines through means that violate the search engines’ terms of service. The term “black hat” originated in Western movies to distinguish the “bad guys” from the “good guys, ” who wore white hats (see white hat SEO). Recently, it’s used more commonly to describe computer hackers, virus creators, and those who perform unethical actions with computers.

Common Black Hat SEO Techniques :

The following SEO tactics are considered black hat and should not be exercised at all if you want to stay above board with Google and other search engines:

Keyword Stuffing : It consists of entering a keyword over and over again on a website or content piece so that the search engine can position for it. According to Google rules, the keyword should always be used naturally and respond to users' needs by providing valuable information or content.

Content Automation : Content automation means using tools or scripts to generate content automatically and publish it on your site without any effort from your side. The automated content is written with no intent for the user, and doesn’t have any format or style whatsoever, without pictures, HTML headings, paragraph spacing, alignment and so on.

Doorway Pages or Gateway Pages : Doorway pages refer to the practice of inflating a site for a particular query in SERP using some cloaking and sending the user on a page that doesn’t have any connection with the query whatsoever. It is an adapted way of redirecting, a more crafty one. Those who use this technique want to rank higher in SERP in an unnatural way, of course.

Cloaking : One of the most important standards of ethical SEO is that websites must appear the same for users and trackers. In the case of cloaking, the trap is to generate a super-optimized website for search engines, but that would be unreadable for a human being. The unreadable website is then cloaked, or covered, with another website designed for users but that is not traceable in search engines.

Hidden text : This SEO black hat practice is very old and violates the regulations of displaying the same content to users and crawlers. It's about hiding texts that repeat keywords over and over by putting the text in the same color as the background or reducing the size.

Reporting a Competitor (or Negative SEO) : The negative SEO does the opposite of what you would expect and that is to cut traffic and decrease SEO visibility continuously.

Redirects  : 301 redirect is actually a good practice. You can use it to send a user from a URL to another one if  the original page has moved or changed. Sadly, over the years, it began to be used as a bad SEO technique.

Link Schemes : Backlinks, or inbound links, are one of the most important factors for positioning a website, but these must be obtained organically. Therefore, purchasing and selling backlinks is considered a black hat SEO technique and is subject to penalty.

Spinning : Spinning is based on "hacking" content creation using programs that modify a single article to generate several different texts, for example, by using synonyms. Logically, this practice does not add any value to the reader, and Google's algorithms are increasingly detecting it faster and more frequently.

Rich Snippet Markup Spam : If you are creating irrelevant Rich Snippets Markup you risk getting manually penalized by Google for this scammy technique.

Social Network Spam : Sending an Enormous List of Irrelevant Links in the Social Network

Automated Queries to Google :  Google's Terms of Service do not allow the sending of automated queries of any sort to our system without express permission in advance from Google.  Sending automated queries consumes resources and includes using any software (such as WebPosition Gold) to send automated queries to Google to determine how a website or webpage ranks in Google search results for various queries.

Guest Posting : Guest Posting Sites List has over 200 high-quality websites or blogs that accept guest posts. Contributing content to the sites in the list will bring organic traffic to your website along with boosting your site rankings. Guest posting is highly effective if done right.  Contact and Submit your content to the list mentioned below and achieve positive results.

Link Manipulation :
a) Link Farm : Manipulating Your Link Profile by Increasing the Number of Inbound Links
b) Linkbait and Switch : Revitalize Your Content into a Commercial One Using Linkbait and Switch Method
c) Link Exchange : Excessive Link Exchange Is Considered a Link Scheme and It Won’t Let Your Site Appear in SERP
d) Spammy Footer Links : Loading the Footer of Your Website with Links Will Only Get You a Large Number of Unnatural Links
e) Web Rings : Building Web Rings to Get Traffic from Related Websites

* Creating pages, subdomains, or domains with duplicate content
* Pages with malicious behavior, such as phishing, viruses, trojans, and other malware
What is Grey Hat SEO?
Grey Hat SEO is the practice of using technically legal methods to improve your site rankings, but which are ethically dubious, and could one day become black hat.

Grey hat SEO falls somewhere in the middle as these tactics are not specifically called out in Google’s Guidelines. Be cautious taking this path as it is not safe to assume that just because a specific technique isn’t labeled or mentioned as being deceptive and one that will get you into trouble, that it will shield you from demotion or penalty.

Although this is a less common term, you’ll sometimes hear SEOs refer to “grey hat” tactics. And as you may have guessed, this term is used to describe strategies that fall somewhere in between white hat and black hat SEO.

In most cases, they could be considered manipulative, but Google hasn’t named them as practices to avoid. So while they might be less risky than the tactics Google has explicitly defined as bad, they still hold the potential for consequences.

For example, tactics like creating doorway pages, building microsites, and submitting to link directories are all considered “grey hat.” You’ll occasionally come across debates about whether these are safe to use, or simply not worth the risk.