It depends which model of Prius you're talking about. The original Prius was a first generation hybrid, meaning it drives on both electricity and petrol. However the electric motor in a Prius makes the petrol engine operate at a much more efficient level, and anecdotally give an efficiency of 4.5 litres petrol per 100 km driven. But, and this is the big but, a original Prius cannot drive without petrol and it has no plug to charge the electric battery. Driving the original Prius charges the electric battery, and there is some regen whilst braking and travelling downhill, which is fed into the electric battery.
However, Toyota do now make a plug-in Prius, the Prius Prime, which makes it a PHEV, but sadly in NZ you see very few on the roads. Toyota has only recently (mid 2017) started selling used / refurbished Prius Prime cars in NZ. These are EVs as they can be driven up to 40km (at last revision) on battery alone, provided you don't go over 105kph, at which point the petrol motor kicks in.
What you can say about a original Prius is that it was a handy stepping stone towards full BEV cars, and it seems mad that Toyota threw away the head start they owned in the early 2000's.