What is the correct term for the type of network created for virtual machines and for containers. For illustration a Linux virtual host might have devices docker0 as 02:42:a6:79:a6:bc with address 172.17.0.1/24 and virbr0 as 52:54:00:b1:aa:1f with 192.168.122.1/24. They are not real networks, correct?
Are they "virtual private networks" i.e. VPNs, or private VLANs, or something else?
Under the hood, all virtualization systems, including docker, use the same mechanism: they use a software switch on the host. Such a switch can be called a "virtual switch" (but this is a bit grey since you now have hardware switches that use a linux kernel and the exact same software to run).
All modern OSes have a built-in, basic, software switch that the virtualization software can take advantage of.
More advanced features can be added to this basic switch implementation, the most common being OpenVSwitch.
Those software switches work exactly the same way hardware switches run, and can handle VLAN, bonding (static or LACP), (x)STP, VxLAN, NetFlow, etc...
By default, desktop virtualization software like VMware Workstation/Fusion or VirtualBox will also perform NAT to use the host IP address for the virtual machine, but you can also configure them for pure bridging (bridge = switch).
So the correct term to refer those networks is either software switch or virtual switch.
There is no specific term (that I'm aware of). A "virtual network," "virtual segment," or perhaps "layer 2 domain" all might be acceptable. You can also look at Docker or Kubernetes documentation to see how they describe it. Whatever terms they use are most likely to be the ones that are accepted.
I'd have called that a "virtual ethernet": there are ethernet addresses, ARP packets, broadcasts. It's virtual because there is no medium.
It's definitely not a VPN, as there is what that is understood to mean is a system where the private leased-lines are virtualised onto shared lines, normally generic internet. While it is clearly some kind of virtual LAN, I wouldn't ever call it a VLAN as it's not virtualising multiple LANs onto a single medium, the normal meaning of VLAN.
