Short for Network Address Translation, NAT as specified in RFC 1631 is an Internet standard that enables a local-area network (LAN) to use one or more IP addresses for internal traffic and a second for external. A network NAT is commonly used by home users to allow multiple computers to easily connect to a broadband connection. NAT is also used to hide Internet network addresses by using the single NAT address.
Today, there are two different variants of NAT used. NAPT, which is short for Network Address Port Translation; and PAT, which is short for Port Address Translation.