Vendasta's Marketplace allows you to market both your own custom products and vetted third party vendor products to your clients and prospects via the Business Center.
A Custom Product is a product or service that you will be providing directly to your clients or prospects. You determine and customize the pricing, the marketing content, and the copy.
A Marketplace Product is a product or service that is provided by an approved third party vendor.
However, there is no discernible difference that your clients will see between a Custom Product designed by yourself and a Marketplace Product.
You can both create your own Custom Products or browse and enable Marketplace Products via the Marketplace > Products tab in Partner Center.