Merge pull request #90409 from seanmck/aks-why2rg

Added better explanation for the node resource group in AKS

Author: PRMerger18

articles/aks/faq.md

@@ -7,7 +7,7 @@ manager: jeconnoc
 
 ms.service: container-service
 ms.topic: article
-ms.date: 07/08/2019
+ms.date: 10/02/2019
 ms.author: mlearned
 ---
 
@@ -55,7 +55,9 @@ For Windows Server nodes (currently in preview in AKS), Windows Update does not
 
 ## Why are two resource groups created with AKS?
 
-Each AKS deployment spans two resource groups:
+AKS builds upon a number of Azure infrastructure resources, including virtual machine scale sets, virtual networks, and managed disks. This enables you to leverage many of the core capabilities of the Azure platform within the managed Kubernetes environment provided by AKS. For example, most Azure virtual machine types can be used directly with AKS and Azure Reservations can be used to receive discounts on those resources automatically.
+
+To enable this architecture, each AKS deployment spans two resource groups:
 
 1. You create the first resource group. This group contains only the Kubernetes service resource. The AKS resource provider automatically creates the second resource group during deployment. An example of the second resource group is *MC_myResourceGroup_myAKSCluster_eastus*. For information on how to specify the name of this second resource group, see the next section.
 1. The second resource group, known as the *node resource group*, contains all of the infrastructure resources associated with the cluster. These resources include the Kubernetes node VMs, virtual networking, and storage. By default, the node resource group has a name like *MC_myResourceGroup_myAKSCluster_eastus*. AKS automatically deletes the node resource whenever the cluster is deleted, so it should only be used for resources which share the cluster's lifecycle.