The parameters elements specified in the ARM template are complex objects themselves. The structure of a parameter is as follows:

"parameters": {
   "<parameter-name>":{
    "type" : "<type-of-parameter-value>",
    "defaultValue": "<default-value-of-parameter>",
    "allowedValues": [ "<array-of-allowed-values>" ],
    "minValue": <minimum-value-for-int>,
    "maxValue": <maximum-value-for-int>,
    "minLength": <minimum-length-for-string-or-array>,
    "maxLength": <maximum-length-for-string-or-array-parameters>,
    "metadata": {
         "description": "<description-of-the parameter>"
      }
   }
}

When you start to deploy the resources, you will be prompted for the input values of the parameters. You can also include the parameter values in another JSON file named templatename.params.json. This will allow you to have multiple versions of the input values for different environments.

The variable elements are in the following form and are defined as a JSON key/value pair and must follow the standard JSON syntax:

"variables":{
   "<variable-name>":"<variable-value>",
    "<variable-name>":{
       <variable-complex-type-value>
   }
}

The following is an example of two variables calling two different functions to obtain the resource group location and assigning a variable to a parameter. Functions are normally encapsulated in square brackets:

"location": "[resourceGroup().location]"
"sbVersion": "[parameters('serviceBusApiVersion')]"

This defines the resource to be deployed or provisioned. The configuration information can either be defined directly in the resource definition or populated from variables and or parameter values:

"resources": [ 
   { 
     "apiVersion": "<api-version-of-resource>", 
     "type": "<resource-provider-namespace/resource-type-name>", 
     "name": "<name-of-the-resource>", 
     "location": "<location-of-resource>", 
     "tags": "<name-value-pairs-for-resource-tagging>", 
     "comments": "<your-reference-notes>", 
     "dependsOn": [ 
       "<array-of-related-resource-names>" 
     ], 
     "properties": "<settings-for-the-resource>", 
     "copy": { 
       "name": "<name-of-copy-loop>", 
       "count": "<number-of-iterations>" 
     } 
     "resources": [ 
       "<array-of-child-resources>" 
     ] 
   } 
] 

The elements are described in more detail here:

The structure of the output element is defined as follows:

  "outputs": {
    "<outputName>": {
      "type": "<datatype-of-output-value>",
      "value": "<output-value-expression>"
    }
  }

The output value can also be used to share state and data between nested template deployments.

Apart from the default elements described earlier, the template can also be extended using expressions and functions. When using functions, it should be enclosed in square brackets.

A full list of the available functions is available from here: https://docs.microsoft.com/en-in/azure/azure-resource-manager/resource-group-template-functions.

They are grouped in the following categories:

These are files used to populate the parameters specified in the ARM template, and they are useful when provisioning Azure resources for different environments or configuration settings:

{
   "$schema": "https://schema.management.azure.com/schemas/2015-01-
   01/deploymentParameters.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        "<name-of-parameter>": {
            "value": "<value>"
        }
    }
}

There are various options available when deploying these templates as listed here: