The Domain Name System is the Internet-standard name service used by Windows 2000 to help clients resolve host names to IP addresses and find services on the network. Before getting into the details of what is new in Windows 2000 DNS, I think we should first review how DNS itself works.
DNS is a distributed system of name servers. In this system, groups of name servers are responsible for records relating to hosts in domains and or subdomains. These groups are called zones. Zones are authoritative, or responsible for, the records relating to a given domain or group of domains. For example, Microsoft might have a few servers responsible for the microsoft.com domain, and all associated subdomains might be part of the same zone. The DNS servers that carry the host records relating to Microsoft.com are said to have authority for that domain. As such, if these servers could not provide an answer for the IP address associated with bluescreen.microsoft.com, it is assumed not to exist.
Name servers hold what are referred to as resource records. A resource record maps a hostname to an IP address, or a particular service to a hostname. For example, a DNS server might contain a host record (called an A record) for a server called server2 that resolves to IP address 147.2.3.45. If a client or another DNS server were to ask for the associated IP address, it would be found and returned. By the same token, a mail server might query DNS looking for the mail server associated with the win2000trainer.com domain. In this case, it is querying DNS for the mail exchanger record (an MX record), which would provide the fully qualified name of the mail server, which could then be resolved to an IP address and contacted.