The private API is a feature that was requested by a buyer.
It consists of an API that is used by the admin to perform actions that can’t be done using the standard API, like expiring a license key so that the customer can’t use it anymore.
The private API calls are performed using the Private API Key.
Using the default Private API Key is not recommended.
The private API key should never be included in anything that a customer has access to, like a WordPress theme, plugin, software that the customer runs on their computer, mobile apps, etc. This API should only be used in code/software that only the admin can access.