This is a non-FreeBSD specific term referring to a Microsoft technology for hostname resolution that can be implemented using Samba. It features in this wiki for reference.
WINS, or Windows Internet Name Server, is a network based service created (somewhat unsurprisingly, given the name) by Microsoft and is their implementation of the NBNS, or NetBIOS Name Server, service.
The WINS service shares similarities to the ubiquitous DNS in that it is a form of hostname-to-IP resolution. It is only capable of resolving NetBIOS based hostnames like LABPC012 and not FQDN based internet hostnames like www.freebsdwiki.net.
Early network implementations that had their origins in mainframes and as such network hosts were few in number. This permitted the use of hostname resolution through hosts text-based files to be used since changes were few and far between.
With the advent of newer technology it soon became possible to buy cheap personal computers to replace large expensive mainframe systems. Maintaining localhost files became impossible with the vast number of hosts on the network which meant hosts had to resort to broadcasting queries to the network in order find other hosts. These broadcasts resulted in saturating the network and every host had to take note of a query to determine whether it had to reply or not, thereby causing computers to run slowly.
It soon became apparent that a service was required that would reduce the network load while making hostname resolution more efficient and quicker. This is where NBNS, and later WINS, came into existence.
The WINS service is very functional on its own but it does rely on other network services with which to make it effective. The following are based on making the WINS service available using FreeBSD as the host operating system:
The WINS service on Unixlike OSes is implemented through Samba. WINS is primarily intended for use on networks that contain many SMB (Windows) network hosts, where an ability to resolve their hostnames without resorting to broadcasting will improve network performance and efficiency.
The DHCP server is capable of sending details of one or more WINS servers as part of an IP address request or renewal, just as it would with default gateway and DNS details. The DHCP configuration option #44, called 'WINS/NBNS' on Microsoft platforms or 'NetBIOS Name Service' on other DHCP implementations, holds the IP addresses for the WINS service hosts.
The other side of WINS is that it tracks hostnames to the IP addresses of hosts on the network that have themselves been given a dynamically allocated IP address from DHCP.
The Samba documentation project has a good description of the WINS service.