A Windows Internet Name Service (WINS) server is a machine that maintains a database of available network resources and the computers that own them. A computer seeking such a resource "asks" the WINS server to look up the address of the machine that owns the resource.
A network can have no WINS servers, or it can have any number of them. See a fuller discussion of WINS in Chapter 5, Chapter 5, Implementing WINS and Maintaining Databases.