When working with Azure Policy, many companies find that they need to create many policies to define all the rules that they want their software developers to adhere to. For this reason, it might be beneficial to group policies. Such a grouping is called an "initiative" and these are defined in JSON as well:

{
  "name": "string",
  "type": "Microsoft.Authorization/policySetDefinitions",
  "apiVersion": "2019-01-01",
  "properties": {
    "displayName": "string",
    "description": "string",
    "parameters": { … },
    "policyDefinitions": [
      {
        "policyDefinitionId": "string",
        "parameters": {}
      }
    ]
  }
}

The body of an initiative is an array of objects. Each object must contain a policyDefinitionId property and, optionally, an object with parameters for the policy. The policyDefinitionId property must reference a valid policyDefintions through its Azure resource ID. The parameters array should specify all of the parameters that the policy requires. Often, this is implemented by having the initiative specify the combined set of all parameters of all policies as an initiative parameter. The parameters for the individual policies are then specified with a reference to the initiative parameters.