Here you can find some distinctions of the backend deployments.
Using the production API and Secret keys will make requests to the live production server. This means that credit cards will actually be processed, and content procured from the vendors. Take care in using these keys, and ensure they're only made use of in a live environment.
Should the SDK be initialized with sandbox keys, all interactions with Guestlogix servers will be through a separate, test only environment. This means that no real credit card numbers will be accepted, booking of products and inventory will not actually be processed. This is useful when testing the application.