The Affidavit of Service tells everyone about the service of the papers. It says:
The Affidavit must be signed by the server in front of a notary public. After the Affidavit of Service is done, it must be filed with the Court.
Proof that legal papers were delivered must always be given to the Court. If the case has started already, the original Affidavit of Service is filed when the original legal papers are given to the Court. The rules are different for filing an Affidavit of Service when starting a case.