Hybrid Vehicle-What is a Hybrid Vehicle

A hybrid vehicle (HV) is a vehicle that uses two or more distinct power or fuel sources such as:

An on-board rechargeable energy storage system (RESS) and a fueled power source for vehicle propulsion
Human or sail powered bicycle with battery assist
A sail boat with electric power[1]
The term most commonly refers to Hybrid-electric vehicle (HEV) which includes internal combustion engines and electric motors (generally powered by electric batteries or other rechargeable energy storage system -RESS-).
History
One of the earliest hybrid vehicles were simply boats with both sails and oars, such as the Greek/Phoenician trireme warships. These used a sail for traveling with the wind, and the oars for when there was insufficient wind, or in circumstances that the sail was unfavorable (such as naval combat, in the case of the triremes).

Hybrid types by engines

Hybrid-electric petroleum vehicles
When the term hybrid vehicle is used, it most often refers to a Hybrid electric vehicle. These encompass such vehicles as the Toyota Prius, Toyota Camry Hybrid, Ford Escape Hybrid, Honda Insight and others. A petroleum-electric hybrid most commonly uses internal combustion engines (generally gasoline or Diesel engines, powered by a variety of fuels) and electric batteries to power electric motors. There are many types of petroleum-electric hybrid drivetrains from Full hybrid to Mild hybrid which offer varying advantages and disadvantages Hybrid fuel (dual mode)
In addition to vehicles that use two or more different devices for propulsion, some also consider vehicles that use distinct energy input types ("fuels") using the same tank and engine to be hybrids, although to avoid confusion with hybrids as described above and to use correctly the terms, these are described as dual mode vehicles:
Some electric trolleybuses can switch between an on board diesel engine and overhead electrical power depending on conditions. In principle, this could be combined with a battery subsystem to create a true plug-in hybrid trolleybus, although as of 2006, no such design seems to have been announced.
Flexible-fuel vehicles can use a mixture of input fuels (petroleum and biofuels) in one tank — typically gasoline and bioethanol or biobutanol, though diesel-biodiesel vehicles would also qualify. Liquified petroleum gas and natural gas are very different from each other and cannot be used in the same tanks, so it would be impossible to build an (LPG-NG) flexible fuel system.
Some vehicles have been modified to use another fuel source if it is available, such as cars modified to run on autogas (LPG) and diesels modified to run on waste vegetable oil that has not been processed into bio-diesel.
Power-assist mechanisms for bicycles and other human-powered vehicles are also included.
A Plug-in hybrid electric vehicles (PHEV) is an emerging type of automobile which can use traditional liquid combustibles and electricity as fuels. Such vehicles could reduce fossil fuel consumption, pollution, and operating costs. If equipped with vehicle to grid technology they could also help stabilize the electric grid by acting as load balance devices. By reducing the amount of liquid fuel required they could also help biofuels meet a larger portion of our fuel demands.

Continuously Recharged Battery Electric Vehicle (BEV)
Given suitable infrastructure, BEVs can be recharged while the user drives. The BEV establishes contact with an electrified rail, plate or overhead wires on the highway via an attached conducting wheel or other similar mechanism (see Conduit current collection). The BEV's batteries are recharged by this process - on the highway - and can then be used normally on other roads.
This provides the advantage of virtually unrestricted highway range. Since most destinations are within 100 km of a major highway, this reduces the need for expensive battery systems.