WinKey -> Bottom row of keys, (Ctrl),(WinKey),(Alt),(SpaceBar),(Alt),(WinKey) on most keyboards.
Normally looks like this ->
IPConfilg/flushdns
Will clear out the current DNS history that your computer uses, forcing it to re lookup any IP Address for websites you're trying to connect to.
DNS Entries are sort of equivalent to Phone Numbers for web sites.
Example you wish to Call John Smith , so you look up in the Phone book and see that their number is 555-555-1234 and save that in your memory.
Well John Smith changes his number, and updates it in the phone book, "IPConfig /flushdns" will make you re-lookup the number and get their new number (555-555-1421) so you can contact them.