In normal situation this broadcast is only limited to the subnet where the machine is located. In this subnet, there will be one machine called Local Master Browser. This machine will catch all the broadcasts (on his own subnet) and build a list with all the machines from which he received a broadcast. Then this list can be exported to all of the machines in the subnet. This list is the one that each machine will use to build the view in the Network Neighbourhood. If you have more than one Workgroup on a subnet, then you will have a Local Master Browser per Workgroup and they'll export browsing list to the other Local Master Browser.
If on a network, there is more than one subnet separated by router which don't let the broadcasts pass, then you will have a Local Master Browser by subnet. If on the same subnet, machines can exchange information by using broadcasts, this is no more the case in a multi-subnet network. At this time, a machine on subnet can only see the other machines on the same subnet. We need now a machine able to collate all the browse lists from each Local Master Browser. This machine is a Domain Master Browser and one must exist for each Domain. To find the Domain Master Browser, you need a WINS server (or a lmhosts file if the Domain Master Browser is the PDC). Remember that the WINS server knows all the machines of the network with their IP address and also the services they are offering. Browser Master, local or domain, are one of these services which can be found in the WINS server. So each Local Master Browser will look into the WINS server for the IP address of a Domain Master Browser to send him their browse list. In exchange, the Domain Master Browser will send a complete browse list of the Domain to each Local Master Browser.
