An Azure virtual network (VNet) is a representation of your own network in the cloud. You can control your Azure network settings and define DHCP address blocks, DNS settings, security policies, and routing. You can also further segment your VNet into subnets and deploy Azure IaaS virtual machines (VMs) and PaaS role instances, in the same way you can deploy physical and virtual machines to your on-premises datacenter. In essence, you can expand your network to Azure, bringing your own IP address blocks. Read the virtual network overview if you are not familiar with VNets.