Backlink is one of important part of website promotion if your link will not be spread so we don't have chance to improve website ranking.
Website backlinks help to improve our website ranking

A “backlink” is one of the most used words in the world of search engine optimization (SEO).Backlinks are incoming links to a webpage.

When a webpage links to any other page, it’s called a backlink. In the past, backlinks were the major metric for the ranking of a webpage. A page with a lot of backlinks tended to rank higher on all major search engines, including Google. This is still true to a large extent.

back links in a simple words it is like voting by other people(websites):) to your site the more healthy votes the more you will get popular

Backlinks are the links from others site to our site.

Backlinks refers for incoming links which refers to all links from other websites. If you are authoritative you are on your topics, the more recommendations you will receive. In some industries, the more backlinks a website has and if they are better links then further up the referring domain will appear in the search results.

Backlinks are like votes for your site to show up in search results, as urls found on other sites.

Dustin Baly

Back-links are inbound hyperlinks to a web site. When a web site hyperlinks to any other web page, it's known as a back-link. In previous times, backlinks were the significant measurement for the position of a webpage