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How it works...
When you use ip or ifconfig, you're querying the network devices that the kernel is aware of, and which it's currently managing the traffic for.
If you don't see your network device in the list output by either of the common commands, it's likely that your kernel doesn't have a driver for the device in question. This is rare these days, but can happen for custom networking gear, whereupon the vendor should supply a kernel module for use with it.
ip itself is more than just one command: it's a suite, meaning that when we used the ip address command here, we were only using a subsection of the tools available to us.
When you use ip route or the route command, you're actually querying the distribution's routing table.