Operating an application in the Sandbox  is essentially the same as operating it in the Production  environment. The main difference is that the application needs to be pointed to the Sandbox environment instead of the Production environment. See the Making a Call documentation for the API you’re using (e.g., Routing the Request in the Trading API docs) for more information on how to point an application to either the Production or the Sandbox environment. 

Sandbox Benefits

• The Sandbox duplicates much of the functionality that is on the eBay Web site. It processes API calls in exactly the same manner as does the Production environment, and it includes a subset of the eBay site’s Web pages. The difference is that all the users are test users (created by developers like you) and all the money exchanged is test money.
• Use the Sandbox to experiment with function calls, to prototype new routines, to test your application’s business logic, and to make sure your application adheres to eBay’s Compatible Application Check Requirements before you actually apply for the Compatible Application Check.
• Before you begin working with the eBay API, and before you attempt to connect to the Sandbox, make sure all the tools in your local development environment work properly.
• Great for testing Buying, Selling and After Sale flows. You will not incur production charges by purchasing and selling items in the Sandbox. We recommend the production for testing searching capabilities.

With the above completed, you are ready to make use of the Sandbox .