Multi Source merchants have one website or a multisite implementation and manage on-hand inventory and fulfilling orders through multiple locations. This is called multi-sourcing.

For example, you have a multisite implementation with websites for United States, Germany, France, and Brazil. Your business includes a number of warehouses and stores in these countries and drop shipper services that manage all inventory stock and fulfill orders. These locations and websites become sources and stocks in Magento. You may create a stock for the Americas and another for Europe, assigning websites and sources based on locales and locations. Customers shopping each website only have access to salable inventories from the assigned sources.