NAT

Maps private addresses to public ones, hiding internal hosts.

Network address translation maps internal private addresses to one or more public addresses, allowing many hosts to share limited public address space while hiding the internal structure from outside view. The obscurity is a side benefit, not a security control, since NAT is not a firewall and does not inspect or filter malicious traffic. It can also complicate end to end connectivity and certain protocols. It is commonly paired with PAT, which multiplexes many internal hosts behind a single public address using ports.