Virtuemart is a idea component to add an eccommerce feature to your Joomla website. Weather you want to simply add a couple of products or 1000s of different products, categories and attributes then Virtuemart is an idea addon.
Virtuemart can manage various shipping methods and zones making sure that the customer is charged the correct shipping depending on the products final delivery address.
It can also manage different currencies and currency convertion by linking into the core exchange rate system.
Again just like joomla you are also able to set the pricing structure for different user levels so you can offer a discount to set goups of users.
Using a dedicated search feature you are able to search though all your products by name, product type, price, category, and pretty much any attribute you decide to set to your products.
Your entire product database can be simply edited and updated using excel and any other spreed sheet application and either uploaded manually to the database or set to automatically update from a dedicated hosted product file.
Using a coupon feature you can add promotional codes that the customer can use to get either a 1 off discount or a perminent discount which can be changed at any time.