VHO are T12 in diameter vs T5 size, so normal floro bulb size you see in ceilings, except these are Very High Output floros and run at 110w for the 46.5" length (4ft) vs the normal 40w. They also have internal reflectors inside the bulbs. They are what people used to use as supplimental lighting/actinics to MHs in the early days. Reason people don't run them by themselves today is because of the diameter, you can fit 2 T5HOs in the same space as 1 VHO, so you get more light out of T5s especially with good reflectors.
Not trying to sound discouraging.. they are still good lights and no reason to run out and replace it all with something else right now. New bulbs may be a good idea though. Since you are just getting into corals then the lighting you have now is fine to start learning with easier corals.