Detailed definition
For Google, a backlink means "other sites are citing your content" = an authority signal. A quality backlink (an authoritative site in your sector, do-follow, highly relevant) has a large effect on rankings. Low-quality backlinks (spam, link farms) can do damage. Ways to earn backlinks: digital PR (press releases, trade media), guest posts, listings in reference directories, content marketing (linkable assets) and partner sites.
Examples
- One do-follow link from Forbes is worth more than 100 links from small blogs.