The Virtual Domains Extension is a very powerful multi-domain management extension. One is able to manage endless numbers of domains from a single Joomla Administrator backend in a very easy way. When the extension is installed and domains entered in the admin panel, Access Levels are created for Menu's, Articles, Modules, templates, you name it. So the access levels are for instance the default Joomla access levels i.e. Guest/Registered/Public/etc but when you have created 'Sitename A' and 'Sitename B' They become also visible in the Articles/modules/menu's/templates and more so it is very easy to assign an article or module or menu to either defined sites or to both through "Guest/Public and more. You can assign different templates/styles to different sites with their own logo and content and menu links.
We have used this now on several sites and it is extremely easy to use. The documentation is not that clear and actual needs improvement but as soon as you are stuck and you send a message to Michael Liebler you will be very friendly and professional assisted with clear explanations. If you have multiple sites with a lot of identical content to manage (multi-shops in several countries for instance or similar multilingual sites with different domain extensions (think .eu/.de/.nl/.com )this tool is a blessing and awesome!