`ifconfig` - configure a network interface (net-tools, deprecated)

ifconfig [interface]

Options you will use

interface: show just that one

Examples

$ ifconfig enp0s1

the old way to see an address

$ ip -br a

the modern replacement

Gotchas

Not installed on Ubuntu Server; sudo apt install net-tools brings it back, but learn ip: ifconfig cannot show multiple addresses per interface properly, policy routing, or network namespaces.

Try ifconfig in a real terminal Free, in your browser - a real Ubuntu terminal to try it in, with missions that check your work.