Definition: A backlink is a link from one website to another. Search engines use backlinks as signals of trust and authority. Now you should not focus on creating backlinks (Quantity), you must focus on the creating quality backlinks.
Getting backlinks from the low quality domains are not going to benefits you even the can harm your website.
Backlinks are generally reference your receive from the third party sites, everyone likes the good reference not the bad, the same happen in the SEO also(Quality) backlinks are good reference of your domain.
Generally there are two attributes of backlinks:
- Do Follow
- No Follow
Example: A marketing blog linking to your SEO article creates a backlink.