How is the urlref defined?


I have a question regarding the urlref.
In some cases, the url ref refers to the previous page to the one on which we land. On the other hand in another case, the urlref does not change, remains the domain of the source of acquisition despite a change of page during navigation of the site.
So my question is: Isn’t the urlref always supposed to be the previous page to the landing page?

thank you

Where can you observe this behavior?