A domain controller (DC) is a server that hosts the Active Directory Domain Services (AD DS) database. AD DS is a directory service that stores information about users, computers, and other objects in a Windows domain. The primary domain controller (PDC) is the DC that holds the authoritative copy of the AD DS database. If the PDC fails, a backup domain controller (BDC) can take over as the PDC.
It is important to regularly check the health of your domain controllers to ensure that they are functioning properly. One way to do this is to check the status of the PDC. There are several ways to check the PDC, including using the Active Directory Users and Computers console, the Netdom command, or the Dcdiag command.