The point is that, while the Volt has a gasoline engine, the engine does not power the car's wheels. The wheels are powered by an electric motor. Batteries for the electric motor can be charged by plugging the Volt into an ordinary electrical outlet.
After the batteries are fully charged, the car can be driven for up to 40 miles without needing additional charging. If batteries do run low, the gasoline engine will run to generate electricity as needed.
The only difference then between the Volt and what you would ordinarily call "an electric car" is that it can charge its own batteries - whenever that may be needed - in addition to using power supplied by your local electric utility.GM has no official on-sale date for the Volt. More research is still needed on the battery, and there's no way to put a timetable on the needed breakthroughs, the company has said.