Hybrid is petrol engine as well as electric motor in the car.
Cost of such a car is definitely more than a normal petrol car, at the same time with huge increase in mileage (obvious since the car runs on motor for sometime)
from
http://automobiles.honda.com/
Q: What is a hybrid vehicle?
A: A hybrid vehicle combines a gasoline-powered engine with an electric motor to provide increased gas mileage and help lower emissions. Specifically, the Civic Hybrid utilizes Honda's Integrated Motor Assist (IMA™) technology, which uses a 1.3-liter VTEC® engine for primary power, then an ultra-thin electric motor provides added power.
as for cost here is an idea....from US market
normal Civic 13k USD, hybrid ~ 20k