The "Air Tube Vehicle" is a concept that involves propelling a vehicle either by suction or pressure.  The vehicle travels along a tube. Either a pressure is applied from behind or a suction from in front.   The concept is the same either way.  The train is propelled by the difference in pressure in front and behind the vehicle.  The vehicle is basically a tube shape that is slightly smaller diameter than the tube it is travelling through.  Remember the old change makers they used to have in department stores like Macy's.  They had these air tubes that carried change and receipts between the cashier and the office upstairs.  The cashier would put your money in a small tube that was then closed and inserted into the air tube which sucked it up to the office where they made change and sent it back through another tube.   There were two sets of tubes going in opposite directions.

 The Transrapid system, run by Siemens, is capable of speeds of up to 450km/h (280mph).

The only commercial example of a Transrapid system in operation is the high-speed shuttle to China's Shanghai airport from the city centre.