Arp (Address Resolution Protocol) resides in the network layer, and its purpose is to reveal information from the hardware layer: the MAC address of connected devices.
It does this by broadcasting a packet through IPs on the network, and devices will send back their MAC address through an ARP Reply message. If a device on the network layer needs a physical address, it will look in the ARP cache or table. One can view this themselves by typing arp -a into their command window.
