Link-building is very important in the SEO to make the website visible in google and traffic on the website. boards,social social bookmarking,directory, weblogs,articles,and news release etc are good for the links.

Best Link Building Methods

Article submission
Blog submission
Content posting
Question Answering
Local business Listing
PPT sharing
PDF submission
Images sharing
Video sharing

Link building process is best way to get backlinks on site and increase traffic and search rank of the sites.

Link building describes various methods that are used to generate links from other websites.
Search engines use links to crawl the web. In this way, Search Engines (e.g. Google) crawls both internal and external links of the web page. The aim of link building is to generate as many links as possible, which are classified by both users and search engines as high-quality and helpful.

so basically, it is very important for a good ranking on the search engine.

Links help to improve your domain authority and page ranking. Please note that if you don't have even one link to your site can also be ranked at the top. The higher number of the links means the best-authorized site and Google will rank your site at the top. There are many link building techniques including article submission, directory submission, blog commenting, drip marketing, infographic submission, and much more. Make sure that the site's to which you submitting are niche sites. Don't build the spammy and toxic links.