Query on ipconfig command line utility options

I am using the ipconfig command line utility to view my current TCP/IP configuration. I understand that ipconfig when used with the option
/release – releases my DHCP configuration
/renew – remews my DHCP configuration
/flushdns – Purges my local DNS cache.
I have done this to get my Internet problem sorted most of the times. But, I recently came across my School System Administrator using these two options on the ipconfig command:
/setclassid and
/registerdns
Can anyone explain me what are they used for? Also, is it equivalent to putting an entry in etc/hosts file?
