This is known as the 'ARP reply'. Once the device that originated the ARP request receives the ARP reply, it extracts the MAC address from the MAC header and updates its ARP table. Now that it has all of the information it needs, the device can properly address its data with both a destination MAC address and a destination IP address. Header - Control information placed before data when encapsulating that data for network transmission. Any device on the network that received the broadcast ARP request sees the information supplied in the ARP request.
Devices use the source information to update their ARP tables.
If devices did not keep ARP tables, the process of issuing an ARP request and an ARP reply would have to take place each time a device wanted to send data to another device on the network. This would be extremely inefficient and could result in too much traffic on the network. To avoid this, each device maintains its own ARP table. Because sending information across networks is dependent on the latest, most current information available, devices are set to delete any information contained in ARP tables that exceeds a particular time limit. Because ARP enables devices to maintain current updated ARP tables, this helps to limit the amount of broadcast traffic on the local network.