Not 100% necessary but it is a kind of source to get a rankings in google.... nearly 77.8% of individual pages in the top results had at least one external link from another site, which means 22.2% of individual pages ranked with no external links
Backlinking is not necessary for ranking, it is mandatory. If you have good enough content, back-linking can occur naturally (other websites will link to your site or pages). In that case, you don't need to build any links.
Backlinks are the impotent factor in google Ranking.but now a days google has started to weed out bad back links from the good links. More number of links will still giving the best result but only if they are coming from different diverse and good domains.
As has been said, depends on competition. If you are short of backlinks, try use the keyword golden ratio (KGR by Doug Cunnington) where you target low hanging fruits with low competition and low search volume. With the Kgr, you get yourself in top 1-100 with no backlinks
I would say, it is good to have some quality backlinks in your profile as it will help in many ways. Not only ranking improvement, if you get them from real site, you can expect some traffic too. Get quality links based on your needs.
Backlinking is the technique of search engine optimization by which you used to put the link/hyperlink of your website on other's website. It is nothing but the inbound link. The links are from your own site to other site and back to your own site that is why it is called as back-linking. Backlinks are important for SEO because some search engines, especially Google, will give more credit to websites that have a good number of quality backlinks, and consider those websites more relevant than others in their results pages for a search query.
Back-link will helps bots to to discover your website and crawl your website effectively. If your website is new then due to back-liking, it helps indexing your website very fast.