How to select framework when build website?

I have got some questions about Dotnetnuke:

• Can i create/run multiple websites having only VS 2010 installed or do i need IIS(Express) ?
• Does a website create a physical map on your harddrive ?
• Can DNN be seen as a SharePoint "alternative" ?
• Once a site is in production can it handle a big workload ?

Thx for any answer.