General Qustions about Installation

Hi

I am new to Netweaver. So my question may look so simple.But i a need an explanation for the following questions.

1) I heard that R/3 4.7 runs on Basis technology. What is this 'Basis' technology.

2) Inorder to setup a portal, I have seen people installing (WAS + Portal) in one machine and (ECC over a system that has WebAS) in another machine. why is a WAS needed for ECC ?. Is it not enough if the first system has WAS installation with Portal over it.

3) What is WinGUI, SAPGUI and ITS. How are all of them related to each other. I know that ITS is used to host webPages.

Good responses will be surely rewarded !!

Murali.