What is the main purpose of back links in SEO and which is the best way to improve our website backlinks.
SEO search engine optimization for any method, ensure that the provided name, a Web site a high ranking in search engines income. If a person is in the business and rely on the income generated from the Web site traffic, it is very important, the site visitor, or click on a lot. That just is not enough to create and publish a website, then the previous high search engine ranking, the results have a way to help your Web site is first obtained in the search list page location. Here, the best way to ensure that the website has good search engine optimization。
Backlinks or Inbound Links (IBL’s) are links that are directed towards your website and are the building blocks to good Search Engine Optimization. The number of backlinks a website has is in a good indicator of its popularity or importance with search engines. Search engines, namely Google, give more credit to websites that have a larger number of quality backlinks and consider those websites more relevant in a search query.
All i know is that it will help on increasing page rank and acquire huge traffic for your site and thats the good thing for that! 
As the previous posters have said backlinks are important for building search engine authority, but much more important than the number of backlinks is the quality of the backlinks. Any fool can set up a thousand free blogs and link them all to one another, however what really counts is the respect commanded by the sites that are linking to you.
Essentially, if sites enjoying a Google Page Rank of 7 or 8 are linking into your site that impresses the search engines and helps persuade them that your site too is worthy of respect.