The Address Resolution Protocol (ARP) is a network protocol used to map an Internet Protocol (IP) address to a physical machine address, also known as a Media Access Control (MAC) address. This process is essential for devices on a local area network (LAN) to communicate with each other, as it allows them to identify the correct hardware address associated with a given IP address. When a device wants to send data to another device on the same network, it broadcasts an ARP request to find out the MAC address corresponding to the target IP address. The device with the matching IP address responds with its MAC address, enabling the sender to encapsulate the data in a frame and transmit it directly to the intended recipient.