Setting up a Virtual LAN is one of the initial tasks when getting started with Hyper-V. It involves dedicating a physical network adapter (NIC) in the host machine to be used by the any VMs you create. You are able to create as many virtual LANs as you have NICs in the server. This process converts any NIC into a virtual switch to be used connected to as many VMS as you like.
As most servers nowadays come with at least 2 NICs built in you are presented with a number of choices for how you utilise them