DNS is an acronym of domain name system. It is simply a mechanic to convert an alphabetic name to a number-based IP address. In a normal practice of using any website what we do is that we simply key-in the address of that website in the address bar of the web browser. But that address is associated with some unique IP address. Here comes the role of a server which results back the IP address of the requested resource such as web page. Any of such server is the one known as DNS server. The synonym used for DNS server is hierarchical decentralized naming system. It includes computer systems, their associated services and various other resources. This system also has a DNS database which holds various DNS names which are associated with some IP addresses.
Protocol-
A protocol is simply a set of rules and guidelines for making the communication among two or more communicating devices. These rules are defined for every process during communication. The communicating computers or devices have to follow the set of rules defined in the form of protocols for the purpose of communication which results in successful transmission of data.
Internet protocol (IP) is the principal set of digital message formats and rules which helps in exchanging messages between computers across a single network or a series of interconnected networks. It takes the help of internet protocol suite known as TCP/IP. In this process, messages are exchanged in the form of datagrams which are also known as data packets or packets simply. The role of IP is the delivery of data from the source host or source computer to the destination computer which is also known as receiving host.