Follow link count as vote of trust and a trust signal for search engine algorithum.
Do follow backlink helps to improve Domain Authority and Page Authority of your website
It improves keyword researches and rank or indexing your content faster
Website give dofollow back link : Web2.0, Guest Post sites, Profile Submisssion sites, News Letter sites, etc....
Paid or sponsord backling must made on website have high DA/PA and spam score less than 20%