In practice
It is a vendor metric, not a Google signal. Use it to compare candidates within one tool, never as a target in a report.
Judge a link source on relevance, traffic and editorial standards first; the score is a shortcut, not a verdict.
Why it matters
Buying links by score is how link profiles fill with high-scoring, irrelevant sites.
Knowing what the number is — and is not — keeps reporting honest with clients and boards.
Related terms