Explanation:
Box 1: New-AzResourceGroupDeployment.
This cmdlet allows you to use a custom ARM template file to deploy resources to a resource group.
For example:
New-AzResourceGroup -Name $resourceGroupName -Location "$location"
New-AzResourceGroupDeployment `
-ResourceGroupName $resourceGroupName `
-TemplateUri "https://raw.githubusercontent.com/Azure/azure-quickstart- templates/master/quickstarts/microsoft.compute/vm-simple-windows/azuredeploy.json" `
-adminUsername $adminUsername `
-adminPassword $adminPassword `
-dnsLabelPrefix $dnsLabelPrefix
Box 2: -ResourceGroupName RG1.
It's one of parameters of New-AzResourceGroupDeployment to specify to which resource group you want to deploy resources.
You could use New-AzVm to create a VM, but it doesn't use a template. You would need to provide all parameters in the command line.
Reference:
https://docs.microsoft.com/en-us/azure/virtual-machines/windows/ps-template
https://docs.microsoft.com/en-us/powershell/module/az.compute/new-azvm?view=azps-7.0.0