This is a video on the command ipconfig and many of the things that it does. Ipconfig can release/renew your IP address It will also show information about your network card. It also allows you to create specialized scope options if you have a Windows DHCP server. It will register your machine with the DNS server and show DNS records stored by your machine.
The command nslookup is a command that allows you to look up dns records. The scary thing about it is that if your DNS is incorrectly configured, then it allows people to scan your entire DNS structure. Also this video states how to allow your machine to perform nslookups with dns forwarding.
This a video about the ping command available in in windows. It can be used to test network connectivity. You send a message to a remote host and then they send a message back that they received it. Sometimes, people will think that their internet is down, but they are still able to ping. That means that something has gone wrong with their browser.