Each different way that customers can order your products is a sales channel. Your own ecommerce site is one sales channel. Third party listing sites, such as Etsy, Ebay, Facebook, and Amazon are sales channels. Direct emails or phone calls from wholesale customers to place orders is a sales channel. Make a list of all these ways you allow people to place an order. Do you have a central place to keep all your open orders so you can track and fulfill them in a reasonable time frame?