Referral process!

Hello! I am a new lvn currently starting work in a clinic. This is my first job as a nurse so the administrative process is still quite new and confusing to me. I have a couple of questions and clarification regarding referrals and the referral process within a clinic. (The nurses here do a lot of the referrals, so far it seems like how the process here is that the pcp would write the order for the referral then task for the nurse to complete the process. (Ex: patient needs stat referral to see a nephrologist, please refer patient out)

So my question is:

1) when a pcp refers a patient out to a specialist how do we know which provider/specialist exactly to refer the patient out to. (So for ex: if a pcp wants a patient to see, let's say a nephrologist how do we know which nephrologist the patient will see so we can properly fax over the papers to that clinic/specialist)

Or

Does it solely depend on the insurance and the clinic itself. As in the clinic usually have a designated specialist that they'll send patients out too? Or will we have to go searching for a nephrologist in that area to see if they take that patients insurance?

Thank you!