Same admin login, but when you create new sites, you will find that you have a whole new setup, like from the beginning, twenty ten theme, just like a fresh install. You can export, then import the main site info through the tools/import/export option, and it allows downloading of files from the main site.
When you get additional sites, you go to them by clicking on “backend” at the site you want to visit in the backend under ADMIN.
Since the sites are generated dynamically, they stay on the same server, you won’t have a whole new site. It is a little different than standard setups.
Same login, same server, but NOT the same media library.
It’s like running a mini-version of WordPress.com 🙂
Thank you very much for your responses.
One other question, If you setup a multisite, can you give certain people access to only one of the site? and if so how do you do that.