Your SEO solution will explain to you that backlinks are public to the users and search engines. Search engines can easily crawl these do-follow type of backlinks. They are permanent one-way profile links. They are not paid links. They contain anchor text which guides a search engine about the content of our webpage or site. Both offpage as well as onpage optimization is necessary to give more PR weightage to your page.
Some website owners use the services of some companies to promote their websites. These companies use their software to promote the site by adding its links to the selected sites. It is unnatural style as your web page must be manually handled with great care and must be linked after hard deliberation to another page (so that to keep its importance, uniqueness and sanctity intact). The automated linking with other web pages can not produce equivalent results.