T5 is the diameter of the bulb and
VHO is the output. It is hard to say what wattage is high, medium or low because it depends on the whole situation. I would characterize NO fluorescent tubes as low light,
PC's as medium and
MH as high. For instance, a 36 watt
PC bulb over a tank that is 10" deep is pretty high lighting but that same bulb over a 36" deep tank is pretty low.
