A "client" is the term used to define a single shopping cart. Certain installations of Cart32 can have multiple "clients" (depending on your license). Multiple clients are useful if more than one shopping cart is needed. For instance if an individual/business has www.website1.com and www.website2.com, they will need a separate client for each website.
The reason behind different levels of "client" licenses is to allow customers to purchase and run multiple shopping carts without installing the software over and over. A single installation of Cart32 can run multiple shopping carts for multiple ecommerce websites (assuming you have a multiple-client license purchased). We offer licenses in 1, 5, 10, or unlimited client versions. For the individual, we recommend the single license version or our Cart32 Hosting service.
Most customers choose to have us, Cart32.com, host their cart for them. This is called Cart32 Hosting and is included in every hosting plan we offer. This is equivalent to a 1-client license of Cart32.