SP API provides two environments: Sandbox Mode and Production.
The SP API Sandbox is a self-contained, virtual testing environment that mimics the live SP API production environment. It provides a shielded space where you can initiate and watch your application process the requests you make to the SP APIs without touching any live accounts.
The SP is invited to join the sandbox, which currently is our Staging environment. As a part of SP invitation to SP API in Staging, we issue an authorization token to this SP. Then, we send a letter to the SP API manager so he would send it to the SP.
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.