Historically, ‘Virtual Channel’ was a term used in the television world, in order to indicate the remapping of a channel (on a specific band) on a ‘fake’ channel more comfortable for the end user to find in his research.
In the IT world, the term indicates the possibility to channel a communication protocol inside a simpler one, to be used in another context. A typical example is the one of the serial protocol. In modern computers the serial port is not used anymore, so in order to use a peripheral device that supports only that protocol is necessary to equip with an adapter able to encapsulate serial packets in usb type ones. The same concept is used in the virtualization world in order to transmit packets coming from usb peripherals on classical nets.