Backlinks (also known as incoming links, inbound links and inward links) are links that point towards your website, from other relevant websites.
Gaining backlinks to your website is an extremely important aspect of boosting your site's rank in Google.
Backlinks are like votes of confidence for your website; the more votes you have - from quality websites - the better your site appears to search engine crawlers.
A single, quality link from a popular site is better than a large amount of poor quality links.