Hi, I've moved the thread to the Wii Basics forum, its a place for new members to ask these kinds of questions and might be worth having a read through some other threads in here.
As for your questions the Virtual Console (VC) is Nintendo’s equivalent to the Xbox live arcade in which users can download many titles from the Nintendo back catalog. This includes titles from consoles such as the N64, SNES, NES and also the Sega Mega drive/Genesis and the TurboGrafx -16.
There has been no official word as of yet about an external hard drive, VC games will be stored on SD memory cards.
Here's a couple of good threads for you to read: