Link building is the process of getting links from other websites to your own. Links are very important to search engines. They use links to find new web pages and to decide on how a page will rank in the search results. A research carried out by Backlinko on search engine rankings revealed that links tremendously influences rankings more than any other factor.
Link building is an art. It's almost always the most challenging part of an SEO's job, but also the one most critical to success. Link building requires creativity, hustle, and often, a budget. No two link building campaigns are the same, and the way you choose to build links depends as much upon your website as it does your personality. Below are three basic types of link acquisition.
QUOTE: “if you want to please Google with your SEO, then forget about SEO. Google wants you to create a site as if you don’t intend to manipulate their algo, but as if you are doing it because your passionate about the topic of your site. If you really are, your content will be great and your target audience will love you, this will do the best possible SEO you can imagine” Andre Weyher, Ex-Google 2012 (disavowed statement by Google)
Spam links often go both ways. A website that links to spam is likely spam itself, and in turn often has many spam sites linking back to it. By looking at these links in the aggregate, search engines can understand the "link neighborhood" in which your website exists. Thus, it's wise to choose those sites you link to carefully and be equally selective with the sites you attempt to earn links from.