NAT maps private IPs to a public IP, obscuring internal topology. Important: NAT is NOT a security control — it provides obscurity but doesn't prevent attacks through forwarded ports or from internal compromised hosts.
"NAT provides security" is a common misconception. Attackers can still reach services via port forwarding. Internal compromised hosts call out through NAT freely. Don't rely on NAT as a security boundary — use firewalls and ACLs.