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The Open System Interconnect (OSI) model for computer networking protocols divides network architecture into 7 layers; Physical, Data-Link, Network. Transport, Session. Presentation and Application. TCP/IP. the most popular networking protocol covers the bottom 4 layers. Within the TCP protocol. there are many other sub-protocols defined. The one I'm writing about is Address Resolution Protocol (ARP).

The term ARP is used in different ways which can lead to confusion. ARP is the protocol used to obtain a computer's data-link address given it's network address. It's also the name of the tool used to manipulate the ARP tables on machines

In order to communicate, each layer of the network architecture needs to have it's own unique address. The data-link address or Media Access Control address (MAC address) is a unique identifier assigned to each network adapter or network interface cards (NICs) by the manufacturer It's an OSI layer 2 address. It looks like a string of 6 bytes. It's commonly written as 8 hexadecimal couplets sepated by colons such as AA:BB:CC:DD:EE The IP address is an OSI layer 4 address. It's 4 bytes long and is commonly written in the form of 4 digits between 0 and 255 separated by colons such as 192. 0.0.1.

Each computer on a sub-net need to keep track of both the MAC and IP addresses of all the other machines on the same sub-net. And also be able to translate the low level MAC address into the higher level IP address.The translation table between ARP and IP addresses for the sub-net is kept in a special file called the ARP table on each machine.

ARP is also the name of a tool that lets you do things like broadcast your ARP address, clear the ARP table, add entries, delete entries and view the ARP table on your local machine. ARP is a command line utility. The most common parameter is -a. It shows the IP address, MAC address and whether the IP address is static or dynamic for each of the adapters..

arp -a ; show me the ARP table on this machine

You delete entries with the -d parameter.

arp -d 102.168.1.1

To view the other options use the /? switch

arp /?