Email campaign unlink a contact

I have a campaign which starts off by sending an email to anyone who has a certain tag applied. The campaign works and creates tasks for us when recipients click on links or buttons in the email.

My question is, when I look at one of the contacts using their normal contact screen, right at the bottom is the contact’s email history which includes the campaign emails. If you click VIEW, it shows you the email, and at the top it lists a few other (seemingly random) other contact names, with an option to unlink them.
These contacts are not linked by us, and don’t appear as linked in their “linked contacts” tab.
What is the link between them, as they seem totally random to us? What is the effect of unlinking them?

Thanks in advance.