An Azure VNet is a virtual representation of a traditional network that's hosted in the cloud. It is totally software-based, whereas traditional networks use cables, routers, and more. VNets provide a secure and isolated environment and they connect Azure resources to each other. By default, the different resources can't be reached from outside of the VNet. However, you can connect multiple VNets to each other or connect a VNet to your on-premises network. All the Azure resources that are connected to each other inside the same VNet must reside in the same region and subscription.

When you create a VNet, one subnet is automatically created for you. You can create multiple subnets inside the same VNet (with a maximum of 1,000 subnets per VNet). Connecting multiple VNets together is called VNet peering. A maximum of 10 peering is allowed per Azure subscription.

The smallest subnet that can be used in Azure is the /29 subnet, which consists of eight addresses. The largest is /8, which consists of 16 million addresses.