When a Windows domain spans multiple subnets each of the subnets has an independent browser called the Master Browser.
The Domain Master Browser is used to collect information from each of the Master Browsers via the NetServerEnum API call.
This merged list is then distributed to the Master Browsers in each subnet so that the enterprise list can be available to computers requesting services.
[1] As part of the Microsoft Windows Server Operating Systems, the browser service is used to host information of other Windows computers within the same Windows domain or TCP/IP network...[2] the Domain Master Browser coordinates browse lists from all the local browsers in a workgroup, no matter what their network segments.
The information, called a Browse List, is held by the browser and primarily consists of the computer names and the services each of the computers offers.