What are the two elements of address translation rules?

Address translation rules are used to map an IP address space into another by modifying network address information in the IP header of packets. Address translation rules have two elements: original packet and translated packet6. The original packet is the packet before it undergoes address translation, and the translated packet is the packet after it undergoes address translation. The original packet and the translated packet may have different source and destination IP addresses, depending on the type and direction of address translation.