Like the Volt, the ELR is a range-extended electric car. Now, you could just call it a plug-in hybrid but GM hates that, and they have a point. The key distinction is that the Volt and ELR run on pure electric power for the first three dozen or so miles before the gasoline engine kicks in.
In most plug-in hybrids the gasoline engine can come on at any time, provided you give the accelerator pedal a hard enough squish. But these cars drive like real electric cars until the battery runs low. Then they start to run like a hybrid car with the gas engine phasing in and out, offering support where needed. Even then, the engine mostly just generates electricity without driving the wheels directly.
The big difference between the ELR and the Volt is that the ELR is tuned more for performance and luxury at the cost of range and efficiency. While the Volt goes 38 miles on a full charge before it starts burning gasoline, the ELR will probably only go 35, according to GM.
