The Address Resolution Protocol (ARP) is used on local networks to resolve IP addresses to MAC addresses. IP addresses are used by the Internet Protocol (IP) to route network packets through the internet. Every network interface card has a hardcoded MAC address. The assignment of IP addresses on a local network is dynamic. Thus a resolution of IP to MAC addresses has to be performed.
The actual IP to MAC address resolution is performed using the stateless ARP protocol. A machine that wants to resolve an IP address broadcasts this request on the local network. The corresponding machine that has the IP address assigned answers this request with its MAC address.
There a several RFC standard documents that define or relate to ARP: