Bring the sales of your products and/or services online with E-commerce. These products can be physical (like a T-shirt) or a digital download (like a PDF book or MP3 song). You can also use e-commerce to make it easy for your customers to pay for your "off-site" services. For example, a Landscaper could have an Ecommerce site where their customers could pay their bill online. Ecommerce can also be used as an auction, similar to Ebay. Your business can now sell to a marketplace that could be national or even worldwide.
Variant Studios uses the Drupal Commerce module to build successful ecommerce websites with an easy to use shopping cart and loads of features.