For questions about Address Resolution Protocol (ARP). ARP resolves OSI layer-3 addresses to OSI layer-2 addresses.
Address Resolution Protocol (ARP) resolves OSI layer-3 addresses to OSI layer-2 addresses. This is necessary because the OSI layers are independent of each other. In order for an OSI layer-3 packet (e.g. IP packet) to be forwarded on an OSI layer-2 protocol (e.g. ethernet), the OSI layer-2 address (e.g. MAC address) must be discovered in order to encapsulate the OSI layer-3 packet into an OSI layer-2 frame which contains both the source and destination OSI layer-2 addresses.