NAT
Network Address Translation — maps private addresses to public ones at a network boundary.
NAT maps private (RFC 1918) addresses to public ones at the boundary, conserving public IPv4 and incidentally hiding internal addressing. It is not a security control on its own — inbound connections are merely unmapped, not filtered — so it must be paired with a firewall. PAT (port address translation) multiplexes many internal hosts onto one public IP and is what home routers do by default.