This grouping represents the IAM Policies API Reference page of the documentation. It is used to control the level of access to your tenancy for individual users that you have added to your tenancy or external organizations with which you have shared access to your Assets and Events.
The first two POST calls are not part of this grouping but are included for convenience to create an Asset and a Location for use by the Policy.
The POST call for creating an Access Policy contains examples of how to set the user or organization that the Policy applies to and how to define what they are able to do. For more detail on Access Policies please see the documentation here for user access and here for organization access.