Which interface is used for VM state and storage migration?

I have a cluster with local and NFS storage for VMs. From what I understand, there are two types of VM migrations:
* VM state (from pve01 to pve02)
* VM storage (e.g. from one NFS storage to another, in between NFS and local storage, etc)

In Web UI, it has datacenter > options > migration settings where I can choose the interface for "migration." which type of migration does it refer to? I am trying to make sure such traffic are not competing with the VM guest traffic.

thank you.