What Is Disavow?
Disavow is a tool that lets site owners formally ask a search engine to ignore specific backlinks when evaluating their site, typically used for toxic or spammy links that can’t be removed directly.
Example
A site owner who discovers dozens of spammy links from unrelated foreign-language domains, and can’t get them removed by contacting the sites directly, can submit a disavow file listing those domains through Google Search Console.
Why it matters
Disavowing is generally reserved for cases of manual penalties or clear, large-scale spam, since search engines have stated they’re generally good at ignoring low-quality links on their own. Overusing disavow on ordinary links can do more harm than good.