I'm surprised but from what I can find there is very little good information on what these really are. Some say they are actually virtual (software interrupts) some say hardware, and a lot say stuff that I at least know is partly untrue. What are these really and how do they work? What is there purpose? Are there actual hardware lines on the motherboard that represent them?
There is no generally accepted, single definition of "virtual IRQ".
It may refer to a software scheme of representing interrupts which abstract physical IRQ's (allowing for sharing of a physical IRQ line by two devices, for instance).
Or it could be something else. For instance, simulated interrupts in a virtual machine. If your Virtualbox gets an interrupt request from its virtual Ethernet card, that can be nothing other than a virtual interrupt request.
Regarding dedicated copper lines on a motherboard: it's more sensible to send a message.
See for instance:
(Is that "virtual IRQ"?)