Internal API provides two environments: Sandbox Mode and Production.
The Internal API Sandbox is a self-contained, virtual testing environment that mimics the live Internal API production environment. It provides a shielded space where you can initiate and watch your application process the requests you make to the Internal API without touching any live accounts.
We strongly recommend you to start in Sandbox Mode and move to the Production Environment only when your application is fully tested and ready to go live. Production is an environment that contains real data and is designed for live integrations. Use this environment only for mature applications that are ready to go live.