This one is about network address translation!
NAT happens because there are not enough IPv4 addresses in the world (like 172.23.1.28) for every computer. So some devices need to hide behind routers because they can’t have their own IPs.
This history of NAT is actually a little more complicated than that – when NAT was introduced, we actually did technically have enough IPv4 addresses for everyone. Some people are grumpy about NAT because the extra indirection makes it hard for computers behind different routers to talk peer-to-peer. (you can read more about NAT traversal if you want to know about that).