Is an Open Source E-Commerce solution (a Component or Plug-in) for the Joomla! Content Management System. It can be run as a Shopping Cart, or in Catalog mode. You need to install Joomla! first (as the "Framework"), and then install & configure VirtueMart.
http://virtuemart.net/features/what-is-virtuemart
http://virtuemart.net/features/what-is-virtuemart