The Chevrolet Volt concept was not referred to as a hybrid at the big show. E-flex was the word in GM advanced plug-in technology propulsion. E-flex or not, the Volt contains both a gasoline engine and electric motor underneath its skin, but is not a hybrid like we now know. In parallel or combined hybrids such as the Prius, the electric motor and gasoline engine work together in an either-or-both-depending-on-what power delivery system. The drive wheels are spun by the gas engine, the electric motor, or both.
The Volt is a series hybrid, which works more like a diesel locomotive. The internal combustion engine in the Volt is not connected to the drive wheels though a transmission. Instead, the engine turns a generator. The engine can either provide electricity to charge up the batteries, or create enough juice to power the electric motor directly, in case the batteries end up like the ones in that flashlight that's been under the kitchen sink since 1977.
We say internal combustion engine instead of gasoline, for the flux of the Volt engine is that it can be swapped out with engines built to run on gasoline, ethanol, methanol, or bio-diesel. The engine can in theory even be replaced outright by a hydrogen fuel cell for those with a solar powered hydrogen conversion setup out back of the garage. In the press release, vice president of research and development Larry Burns said that this means international fuel source flexibility, and that the Swedes could even use wood methanol to power the Volt. He said wood.