Hello.

It depends. You can install every site into new Kentico CMS instance, or you can have all sites under one Kentico CMS instance. In first case, every site will have its own database, project folder, etc. In second case, you can share global objects between sites. And yes, every site needs its own domain name (and license key).

You can find next info in our Developer´s guide (http://devnet.kentico.com/docs/devguide/index.html?friends_settings.htm), chapter Managing sites and settings.

Best Regards,
Radek Macalik