Because these types of vehicles don’t consume fossil fuels such as petroleum

Because these types of vehicles don’t consume fossil fuels such as petroleum, they do not produce any tailpipe emissions.
PHEVs (plug-in hybrid electric vehicles), on the other hand, are fuelled primarily by gasoline and only supplemented with battery and motor for better efficiency.
In PHEVs, a battery, which can be plugged into the electric grid for charging, is used to power an electric motor, while gasoline drives the internal combustion engine. Certain types of plug-in hybrid electric vehicles are also known as extended-range electric vehicles (EREVs).
Often times, PHEVs utilise electricity for shorter ranges (around 9.6 to 64.3 km). Once the battery is depleted, they switch to the internal combustion engine for greater speed and range. More eco-friendly varieties of plug-in hybrids, at times, use hydrogen fuel cells, biofuels or some other kind of alternative fuel in place of gasoline.
There is a third category: conventional hybrids such as Toyota Prius, which is fitted with a petrol tank and also has a battery that gets charged every time the vehicle brakes.
A hybrid vehicle uses two or more distinct types of power, such as internal combustion engine to drive an electric generator that powers an electric motor
When the term hybrid vehicle is used, it most often refers to a Hybrid electric vehicle. These encompass such vehicles as the Saturn Vue, Toyota Prius, Toyota Yaris, Toyota Camry Hybrid, Ford Escape Hybrid, Toyota Highlander Hybrid, Honda Insight, Honda Civic Hybrid, Lexus RX 400h and 450h and others.
A hybrid most commonly uses internal combustion engines (using a variety of fuels, generally gasoline or Diesel engines) and electric motors to power the vehicle. The energy is stored in the fuel of the internal combustion engine and an electric battery set. Vehicles as the Saturn Vue, Toyota Prius, Toyota Yaris, Toyota Camry Hybrid, Ford Escape Hybrid, Toyota Highlander Hybrid, Honda Insight, Honda Civic Hybrid, Lexus RX 400h and 450h are some of the hybrid vehicles.
There are many types of hybrid drive trains which offer varying advantages and disadvantages.
Parallel hybrid
In a parallel hybrid vehicle an electric motor and an internal combustion engine are coupled such that they can power the vehicle either individually or together. Most commonly the internal combustion engine, the electric motor and gear box are coupled by automatically controlled clutches. For electric driving the clutch between the internal combustion engine is open while the clutch to the gear box is engaged. While in combustion mode the engine and motor run at the same speed.
The first mass production parallel hybrid sold outside Japan was the 1st generation Honda Insight.

Mild parallel hybrid
These types use a generally compact electric motor (usually