Network Address Translation - mostly to map local IPs to public ones, but sometimes used to map between two public or local networks.
This article is about ARP protocol. It’s used to map IP addresses to physical (MAC) addresses.
ICMP protocol is needed for troubleshooting. For an TCP/IP stack here is what ICMP request looks like in a frame:
This article is about IP protocol (v4, v6 and IPX). IPv4 Number on top and along the left edge are bits (not bytes).