Link building is the practice of creating unidirectional hyperlinks (also known as “backlinks”) to a website in order to improve visibility on search engines. It is the process of acquiring hyperlinks from other websites to your own, which search engines use to crawl between individual pages on your website and between multiple websites. Link building is the work involved in investing in backlinks, whether you're building networks or buying them. The goal of link building is to increase referral traffic and the authority of a website.
Search engines track the number of links to your site and give you a score called PageRank, which influences the health of your SEO. Common link building strategies include content marketing, creating useful tools, email outreach, creating broken links, and outreach to other websites and blogs in your niche. Being transparent with your link building campaign can help you win the backlink and show the webmaster that you're not a shady marketer. Links are still one of the most important ranking factors used by Google and other search engines.
With natural links, you'll appear higher in the SERPs and make yourself known within your online community. A large number of high-quality, relevant links is an excellent indicator that your website has a strong backlink profile. To make it easier to understand, you can view a link as a positive vote, and the more votes (links) you have on your website, the better your ranking will be. Personally, I don't recommend building links with a black hat (the risk doesn't come close to justifying the reward).