This ARM template shows how to use conditions and logical/comparison functions to dynamically create windows/linux for prod/non-prod

vmCondition

{
    "$schema": "http://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        "vmNamePrefix": {
            "type": "string",
            "defaultValue": "VM",
            "metadata": {
                "description": "Assing a prefix for the VM you will create."
            }
        },
        "production": {
            "type": "string",
            "allowedValues": [
                "Yes",
                "No"
            ],
            "metadata": {
                "description": "Select whether the VM should be in production or not."
            }
        },
        "platform": {
            "type": "string",
            "allowedValues": [
                "WinSrv",
                "Linux"
            ],
            "metadata": {
                "description": "Select the OS type to deploy."
            }
        },
        "userName": {
            "type": "string",
            "defaultValue": "azureadmin",
            "metadata": {
                "description": "Specify the OS username"
            }
        },
        "pwdOrssh": {
            "type": "securestring",
            "metadata": {
                "description": "If Windows, specify the password for the OS username. If Linux, provide the SSH."
            }
        }
    },
    "variables": {
        "vNetName": "vnet01",
        "subnetName": "subnet1",
        "vNetAddressPrefix": "192.168.0.0/16",
        "subnetAddressPrefix": "192.168.0.0/24",
        "vnetID": "[resourceId('Microsoft.Network/virtualnetworks', variables('vNetName'))]",
        "subnetRef": "[concat(variables('vnetID'),'/subnets/', variables('subnetName'))]",
        "windowsOffer": "WindowsServer",
        "windowsSku": "2016-Datacenter",
        "windowsPublisher": "MicrosoftWindowsServer",
        "linuxOffer": "UbuntuServer",
        "linuxSku": "12.04.5-LTS",
        "linuxPublisher": "Canonical",
        "availabilitySetName": "[concat(parameters('platform'), '-', 'avset')]",
        "availabilitySetId": {
            "id": "[resourceId('Microsoft.Compute/availabilitySets', variables('availabilitySetName'))]"
        },
        "vNicName": "[concat(parameters('platform'), '-', 'nic')]",
        "pNicName": "[concat(parameters('platform'), '-', 'pip')]",
        "vmName": "[concat(parameters('vmNamePrefix'), parameters('platform'))]"
    },
    "resources": [
        {
            "apiVersion": "2017-04-01",
            "type": "Microsoft.Network/virtualNetworks",
            "name": "[variables('vNetName')]",
            "location": "[resourceGroup().location]",
            "properties": {
                "addressSpace": {
                    "addressPrefixes": [
                        "[variables('vNetAddressPrefix')]"
                    ]
                },
                "subnets": [
                    {
                        "name": "[variables('subnetName')]",
                        "properties": {
                            "addressPrefix": "[variables('subnetAddressPrefix')]"
                        }
                    }
                ]
            }
        },
        {
            "type": "Microsoft.Network/publicIPAddresses",
            "apiVersion": "2017-04-01",
            "name": "[variables('pNicName')]",
            "location": "[resourceGroup().location]",
            "properties": {
                "publicIPallocationmethod": "Dynamic",
                "dnsSettings": {
                    "domainNameLabel": "[toLower(concat(parameters('vmNamePrefix')))]"
                }
            }
        },
        {
            "type": "Microsoft.Network/networkInterfaces",
            "apiVersion": "2017-04-01",
            "name": "[variables('vNicName')]",
            "location": "[resourceGroup().location]",
            "dependsOn": [
                "[resourceId('Microsoft.Network/publicIPAddresses/', variables('pNicName'))]",
                "[resourceId('Microsoft.network/virtualNetworks/', variables('vNetName'))]"
            ],
            "properties": {
                "ipConfigurations": [
                    {
                        "name": "ipconfig1",
                        "properties": {
                            "privateIPAllocationMethod": "Dynamic",
                            "publicIPAddress": {
                                "id": "[resourceId('Microsoft.Network/publicIPAddresses', variables('pNicName'))]"
                            },
                            "subnet": {
                                "id": "[variables('subnetRef')]"
                            }
                        }
                    }
                ]
            }
        },
        {
            "condition": "[equals(parameters('production'), 'Yes')]",
            "type": "Microsoft.Compute/availabilitySets",
            "apiVersion": "2017-03-30",
            "name": "[variables('availabilitySetName')]",
            "location": "[resourceGroup().location]",
            "properties": {
                "platformFaultDomainCount": 2,
                "platformUpdateDomainCount": 3
            },
            "sku": {
                "name": "Aligned"
            }
        },
        {
            "type": "Microsoft.Compute/virtualMachines",
            "apiVersion": "2017-03-30",
            "name": "[variables('vmName')]",
            "location": "[resourceGroup().location]",
            "dependsOn": [
                "[resourceId('Microsoft.Network/networkinterfaces/', variables('vNicName'))]",
                "[resourceId('Microsoft.Compute/availabilitySets/', variables('availabilitySetName'))]"
            ],
            "properties": {
                "availabilitySet": "[if(equals(parameters('production'), 'Yes'), variables('availabilitySetId'), json('null'))]",
                "hardwareprofile": {
                    "vmsize": "Standard_D1"
                },
                "osProfile": {
                    "computername": "[parameters('vmNamePrefix')]",
                    "adminusername": "[parameters('username')]",
                    "adminpassword": "[parameters('pwdOrssh')]"
                },
                "storageProfile": {
                    "imageReference": {
                        "publisher": "[if(equals(parameters('platform'), 'WinSrv'), variables('windowsPublisher'), variables('linuxPublisher'))]",
                        "offer": "[if(equals(parameters('platform'), 'WinSrv'), variables('windowsOffer'), variables('linuxOffer'))]",
                        "version": "latest",
                        "sku": "[if(equals(parameters('platform'), 'WinSrv'), variables('windowsSku'), variables('linuxSku'))]"
                    },
                    "osdisk": {
                        "name": "[concat(parameters('platform'), '-osDisk')]",
                        "createOption": "FromImage",
                        "managedDisk": {
                            "storageAccountType": "Standard_LRS"
                        },
                        "caching": "ReadWrite"
                    }
                },
                "networkprofile": {
                    "networkinterfaces": [
                        {
                            "id": "[resourceId('Microsoft.Network/networkinterfaces', variables('vNicName'))]"
                        }
                    ]
                }
            }
        }
    ],
    "outputs": {
        "vmEndpoint": {
            "type": "string",
            "value": "[reference(concat(variables('pNicName'))).dnsSettings.fqdn]"
        },
        "platform": {
            "type": "string",
            "value": "[parameters('platform')]"
        },
        "connectionInfo": {
            "type": "string",
            "value": "[if(equals(parameters('platform'), 'WinSrv'), 'Use RDP to connect to the VM', 'Use SSH to connect to the VM')]"
        }
    }
}

Very simple to understand examples and well explained!!

I have a question. In this example we have two options: WinSrv and Linux. And using the If we say if WinSrv then WinSrv else Linux.

But what function and how can be used for dealing with three options? So, option1, option2, option3
Can this be done without a case statement function?

@webyxdesign you can do something like this:
[if(equals(parameters('options'),'Option1'),Option1,if(equals(parameters('options'),'Option2'),Option2,Option3))]

Where options is your parameter name.
This example basically is an if, else if, else kind of conditional. if false, do an if again, and if false, do another if....
To simplify:

if options == 'Option1':
      print('Option1)
 elif options == 'Option2:
     print('Option2')
else:
    print('Option3')