Network Address Translation (NAT)

Network Address Translation, NAT, was created in order to increase the lifespan of IPv4, along with RFC 1918 addressing rules. It allows a host within a Local Area Network (LAN) to use an internal address, while still allowing this host to access external services - in does this by translating the internal address to an external address.

This allows a large LAN of many hosts to use just one public IP address.