GET requests sometimes retrieve associated resource objects. For example, Payment attributes may include associated Authorization objects and Capture objects.
By including the expand parameter in your request, you can retrieve the full set of attributes for selected associated resources. Enter a list of resources to expand, or 'all' to expand all associated resources.
For example, to expand the Payment Method resource returned in a GET payments request, add the following to the end of the request, ?expand=payment_method.
The best practice is to ?expand=all.
See example screenshot below: