I think you mean “authority” link. The concept of authority applies to a site that is useful and has built up significant value wrt the factors that influence off page and on page search engine optimization.
Domain authority consists of dozens of factors, as does page authority — but the most basic of domain/page authority factors is the combined value of the value-passing inbound links to the domain.
The easiest rule of thumb for the inbound link aspect/factor’s role in authority is to ask, “how strong/important is the sum of the inbound links to this page/domain in their overall collective of rankings in the search engines?”
A simple example would be the premise of receiving a link from A) a brand new site that has no links and power versus B) receiving a link in relevant context from a very valuable site that has been around for a long time and is considered an ‘authority’ on the topic which your site covers or where the link is extremely helpful and logically linked from that authority.
In that example, B would provide your site/page with much more value.
Hope this helps!