Diagnostics and advanced options
The Advanced tab lets you update to Ephemeral OS disks, which only save to the local VM storage and work great for stateless workloads, as they don't save to Azure cloud storage.  Once you've made these decisions, you then progress to virtual networking. A VNet is then used to connect to the network interface (NIC) and the Azure cloud.
If a VNet already exists in the resource group, location, and subscription tenant, then a VM can use it. This will mean you won't have to deploy a new one just for the VM. Workload traffic should be discussed as part of the decision to use an existing VNet or deploy a new one as part of the VM.
The VNet will deploy public and private IP addresses to be used by the VM for access. These addresses must be associated with the VM by assigning them to the NIC. Inside each VNet, there is a subnet (or subnets) that follows rules for allocating traffic in and out of the VM. If a rule hasn't...
