Like with WordPress MU you can also run one Joomla core with several websites. This allows you to have several domains pointing to your webspace, and each domain having a different theme, and content. Configured correctly you can even run all the sites on one database. All our plans support this however you need to be aware the multisites on a shared server is not long term solution. If you have a few low volume sites, then this is for you, however if the sites get busy its not just the bandwidth you need to worry about it the server usage.
