NAT stands for Network Address Translation. This is a technique that lets multiple machines on one side of your router share a single internet connection and internet IP address. The router does this by handing out local IP addresses to each machine on your local network, and translating between those addresses and the “real” internet IP address when the local computers access the internet.
Curious how it works? See the Ask Leo! article: How does NAT work?« Back to Glossary Index