Canonical URL
A declaration naming which URL is the real address of a page, so duplicate variants do not compete with each other.
What it means
Trailing slash or not, www or bare, with or without tracking parameters, printed version, AMP version. A page usually has more addresses than anyone intended. The canonical link element names the one that counts.
The part a short definition leaves out
A canonical pointing at a different domain hands credit for the page to that domain. That is exactly right for syndicated content and a serious error everywhere else, so QuickRankAI reports it and lets you decide rather than assuming.
Where this comes from
See whether this is costing you anything
The inspection reports on this signal directly, alongside thirty-seven others, and tells you whether it is a quick fix on your site or something deeper.