A backlink is a link from one website to another that indicates the quality and relevance of the content on the linked site. Backlinks are important for SEO because they help search engines determine which sites are trustworthy and popular for certain keywords.

A good backlink comes from a high-authority, relevant, and trustworthy site that uses your target keyword in the anchor text. A low-quality backlink comes from a low-authority, irrelevant, or spammy site that uses generic or unrelated anchor text.