PAN-OS REST API
Documentation for the REST API can be found here, within the official technical documentation for PAN-OS.
Of particular interest would be the Getting Started with the REST API guide.
A key resource when using the REST API is the on-device documentation. This can be found at
HOSTNAME should be replace with the IP address or hostname of your PAN-OS appliance. The documentation will also be version-specific to the PAN-OS software currently running on the appliance.
It is also strongly advised that you read about the differences between the XML API and REST API, to make an informed decision on which is most appropriate for your given use case(s).