Domain Name Service (DNS)
The function of the DNS service is to resolve hostnames, such as server1.xyz.com, to IP addresses. Such a resolution system makes it possible for people to remember the names of, and refer to frequently used hosts, using the easy-to-remember hostnames rather than the hard-to-remember IP addresses.
Similar to other TCP/IP-based services, DNS is a platform-independent protocol. Therefore, it can be used on Linux, UNIX, Windows, NetWare, and almost every other platform.
On networks where there is no DNS server, it is possible to resolve hostnames to IP address using the HOSTS file; however, such environments are becoming increasingly rare. All common network operating systems now include DNS server application software.
The HOSTS file is a text file, found on almost all PC operating systems, in which you can place hostname-to-IP-address resolution information. When HOSTS files are used, it's up to the administrator to manually make changes to the file if needed.
This factor alone is sufficient to make the installation of a DNS server an obvious choice.