Link Building is the process of acquiring backlinks to a website for the intention of increasing SEO and traffic.
There is controversy as to the importance and validity of link building. In their Webmaster Guidelines, Google urges people to not build links unnaturally. The controversy appears to be over what is natural and unnatural.
Increasingly, fewer webmasters are linking to other websites when asked. They are more likely to share the content on social media. Or they are suspicious of the webmaster asking for a link. As a result, link building is ineffective and should be avoided.
A better strategy than link building is “link baking.” Link Baking is the process of including subjects in your content while you create it. This often results in that subject linking to the article from their website. But at no time should you ask for a backlink, it should be naturally earned as part of the link baking.
Link building in various forms is considered a black hat or gray hat SEO tactic.