Backlinks show search engines, like Google, that your website is worth reading and that it is informative.
Many search engine algorithms look for quality Best Backlinks from reliable, related sites when they're trawling the web for sites to include at the top of results pages. If your website has lots of quality links from relevant sources, then it's likely to rank higher than a website or page with fewer links.
There are other criteria, such as traffic and keyword usage, so you have to make sure that every aspect of your SEO is strong, as well as building quality backlinks.