The PayPal Sandbox is a self-contained, virtual testing environment that mimics the live PayPal production environment. It provides a shielded space where you can initiate and watch your application process the requests you make to the PayPal APIs without touching any live PayPal accounts and settings. Before you can integrate a PayPal product or solution, you must set up your development environment to get OAuth 2.0 client ID and secret credentials for the sandbox and live environments. You exchange these credentials for an access token that authorizes your REST API calls. To test your web and mobile apps, you create sandbox accounts. This Auth0 integration allows you to test your PayPal solution end-to-end.