I’m not at a Linux machine at the moment, but ip a is probably short for “ip addr”, which shows the local machine’s IP address with iproute2 (historically, one would have used OP’s ifconfig).

I dunno -d off the top of my head, but du -h shows, using “human readable units” — like “M” for megabyte, etc, the size of all the files below each directory starting at the current one. It pairs well with sort -h, which can sort those units — du -h | sort -h is a nice way to get an overview of what is eating up your disk space.