When you install Hyper-V on a system and you select a network adapter for virtual machines some changes will be made to your configuration. Before installation of Hyper-V, I had the following connection:

I had only one adapter because I used a standard HP desktop. The adapter was configured with a static IP. During installation, I chose the above adapter for virtual machine networking (click to enlarge):

After the reboot when the installation is complete, the network adapter configuration changes. In my case:

Local Area Connection is the same as before. It represents the physical network adapter in the system. But the configuration only has the Microsoft Virtual Network Switch Protocol configured. IPv4 and other configuration settings are not active anymore:

The Local Area Connection 3 adapter is actually a virtual adapter that is available to the parent partition (the actual installed operating system running on top of the hypervisor) for management. You set the IP address for your physical machine there. This virtual adapter is actually bridged over Local Area Connection just like a virtual machine.

When you disable the network adapter that represents the physical adapter (Local Area Connection in my case), virtual machines and the parent partition will lose connectivity. When you disable only the virtual network adapter of the parent partition (Local Area Connection 3 in my case), you will lose network access to the parent partition but your virtual machines will still have access to the network. This is because they still have their virtual interface bridged over the physical adapter.