ARP is an acronym stands for Address Resolution Protocol.
The term address resolution specifies that how a process finds an address of a computer in a network. It is used by the Internet Protocol (IP) [RFC826], specifically IPv4. It is mainly used to map IP network addresses to the hardware addresses used by a data link protocol. It is used when IPv4 is used over Ethernet.
The address resolution protocol operates below the network layer as a part of mediator between the OSI network and OSI link layer. It resolves the address using a protocol which receives information sent by a client process executing on the local computer to a server process executing on a remote computer. The information received by the server facilitates the server to uniquely identify the network system for which the address was required and therefore to provide the required address.
The address resolution procedure is completed when the client receives a response from the server containing the required address.
There are four types of ARP messages that are sent by the ARP protocol.