What is a backlink?
Backlinks represent the links from third-party domains that point to your domain and pages. A "backlink" is any link to your site placed on an external website. It could be easily defined as the opposite of a outbound link, as it is created when another website links to your pages.
A backlink is often called inbound link or external backlink as well. The number of backlinks or referring domains contribute to the web site's rank and relevance. The higher the number of backlinks, the better! A website can have multiple backlinks from the same referrer site, as long as the linked content is relevant and useful for the reader. However, ideally, backlinks from multiple referring sites are the best for website ranking, as they work as a vote of trust for the content on the linked page.
The more outside sources trust you; the more loved you are by the ranking algorithms!