什么是Backlink？
A link from another website to yours. Search engines treat backlinks from relevant, reputable sites as endorsements that help rankings.
A backlink is a link from someone else's website to yours. Search engines treat them as endorsements: a site linked to by many relevant, reputable pages is presumed more trustworthy, and that presumption has been central to Google's ranking since PageRank. Backlinks remain one of the stronger inputs to keyword ranking.
Quality beats quantity by a wide margin. One editorial link from a respected industry site outweighs hundreds of directory listings, and links carrying rel="nofollow" or from link farms pass little or no value; buying links at scale risks penalties. Sustainable acquisition is mostly a content problem: publish things worth citing (original data, genuinely useful tools, definitive guides), then do outreach, guest writing, and digital PR to put them in front of people who link. Aggregate link strength is what domain authority scores attempt to estimate.
You can watch backlinks arrive indirectly in your analytics as referral traffic, though most links send few visitors directly; their value is the rankings they support.