DNS server stands for "domain name system" server, and it refers to a computer that translates text-based website names into hexadecimal IP addresses. An IP address refers to the physical address of a device within a network using TCP/IP protocol.
In most cases, a person types in the alphabetic name of a website he wants to visit in an Internet browser's address bar. The DNS server then looks up the numerical address of the website in a database of IP addresses, called DNS record, to locate the website. The Internet browser then returns the query to the requester.
IP addresses allow devices to communicate within a network and the Internet. Without a DNS server to translate domain names into text-based names, humans need to remember the exact hexadecimal names of websites. DNS servers are also responsible for mapping domain names and assigning numerical IP addresses to domain names.
There are several types of DNS servers on the Internet, and each type of server performs a different function. Each server type is categorically assigned a specific class of service by the domain name system. The protocol is designed in this way to avoid DNS server-request congestion that can slow down Internet traffic.