I don't know this is on-topic question. But I have this question as a webmaster.

My site is abc.com. xyz.com site link to my site and a user coming via xyz.com to my site.

My question is how Google Analytic find this user coming via xyz.com link.

My site is abc.example. xyz.example links to my site. Google Analytics reports that users come via xyz.example to my site.

How does Google Analytics know that users have come from the link on xyz.example?