How it works
IPv4 addresses look like 203.0.113.7: four numbers from 0 to 255, about 4.3 billion addresses in total, which the world ran short of years ago. IPv6 addresses look like 2001:db8::1 and are 128 bits long, enough to give every device its own address many times over. Many networks now run both side by side.
A public address can be reached across the internet. Private ranges such as 192.168.x.x and 10.x.x.x are reused inside homes and offices, and the router shares one public address between them through NAT (network address translation). NAT is why a home server cannot be reached from outside without port forwarding, and why video calls need helpers such as STUN and TURN servers to connect.
Devices usually get their address automatically from the router through DHCP, and DNS turns names such as example.com into addresses. An address shows roughly where a device connects from, which is how websites guess a visitor's country, but it does not pinpoint a person.
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