Authentication with the API is done using API keys. For API requests, the API key can be sent along in the headers. The header key for this is x-api-key.
The TEST API keys should be used for testing your integration. Keys are not scoped to live/test orders but are rather meant to safely make orders. Without worrying about them getting billed to your account.
The only difference between a LIVE and a TEST API key is that the orders you make with a TEST key will never be printed and sent.
When you enter an order with a LIVE key, it will be printed and sent automatically. We cannot cancel or hold back orders, so please use the LIVE API key carefully and do not share it with others.
You can create multiple API keys yourself and give them a name/reference.