One of the roles of machines running Microsoft Windows NT and Windows 2000 in supporting the computer browser service on a Windows NT–based or Windows 2000–based network.
The domain master browser is a computer running Windows NT or Windows 2000 that collects the master list of domain resources on the network.
It then distributes this list to master browsers on each subnet. If the domain has only one subnet, the domain master browser is also the master browser for that subnet.
A Windows NT domain has only one domain master browser, which is always the primary domain controller (PDC).