Common uses could be synchronizing product inventory, or sending orders to a fulfillment company. Download the documentation from this link.
https://www.corecommerce.com/docs/pdf/CoreCommerce-API-Documentation.pdf
To configure your API account in CoreCommerce, navigate to Settings
From there, please create the Username, Password, and XML Key you wish to assign to your store. These values are created by you and are used to validate your API script when you connect to the API from your outside script. See below for a screenshot of the API config screen in your CoreCommerce Admin Panel.