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A hybrid car features a small fuel-efficient gas engine combined with an electric motor that assists the engine when accelerating. The electric motor is powered by batteries that recharge automatically while you drive.

There are two types of gasoline-electric hybrid cars: the parallel hybrid and the series hybrid. In a parallel hybrid car, a gasoline engine and an electric motor work together to move the car forward, while in a series hybrid the gasoline engine either directly powers an electric motor that powers the vehicle or charges batteries that will power the motor.

Hybrid cars also gain efficiency from:

Smaller and more efficient engines.
Regenerative braking - the electric motor that drives the hybrid can also slow the car. In this mode, the electric motor acts as a generator and charges the batteries while the car is slowing down.
Periodic engine shut off - when a hybrid car is stopped in traffic, the engine is temporarily shut off. It restarts automatically when put back into gear.
Advanced aerodynamics - to reduce drag
Low-rolling resistance (LLR) tires - narrow, stiffer tires have less drag
Lightweight materials - increases the efficiency of hybrid cars.

Hybrid cars cost more than their non-hybrid counterparts, but due to steady gains in technology, the hybrid price premium is coming down. New affordable hybrid sedans, and improved versions of existing hybrids, are expected to at least double hybrid market share in the next five years, from about 2.5 percent in 2010 to 5 percent or higher in the next five years.

A more recent development in hybrid technology is "plug-in" hybrid cars. These models offer the same benefits as hybrid cars, with the added benefit of being able to be plugged in to home electric outlets for recharging when the car is not in use. This extends the range for the"electric-only" driving mode, leading to increased mileage and fuel savings.