Address translation, specifically Network Address Translation (NAT), can be used to hide one or more devices behind a router or firewall that is performing NAT. This enables us to extend the life of IPv4 because a single globally routable IP address can support thousands of private IP addresses being translated to a single IP address. To do this, a subset of NAT called Port Address Translation (PAT) is used.
NAT allows private IP addresses (as defined in RFC 1918) to be translated into Internet-routable IP addresses (public IP addresses).