A car is a road automobile used to carry passengers (people).  Cars usually have four wheels (round things which turn in order to lead to movement), and an engine or motor to make them move.

Cars are also called automobiles, which comes from the Greek prefix "αυτό" (auto) and the French word "mobile". This name means "self-moving", as cars run on their own power and do not need horses or other power from outside to move.

Like other automobiles, cars are made in different shapes and sizes, for people with different needs. Here are some common types of cars.

To make a car move, it must have energy to turn the wheels.  This energy might be chemical energy in gasoline or electrical energy in a battery. How quickly the engine or motor can send the energy to the wheels, and how much energy is sent, is called the power of the motor. The power of a car is usually measured in kilowatts or horsepower.

As of 2019, most cars burn a fuel to make an internal combustion engine (sometimes called a "motor") run. The power from the engine then goes to the wheels through a transmission, which has a set of gears that can make the car go faster or slower. The most common fuel is petrol, which is called "gasoline" or "gas" in American English.

Gasoline is called a fossil fuel because it comes from tiny fossils that were made millions of years ago. Over millions of years, they turned into oil, which was then drilled up from deep inside the Earth, and then turned into fuel by chemical changes. Old gasoline-powered cars are noisy and their exhaust makes city air dirty, which can make people ill. But cars made after the mid-2010s are cleaner.[1]

Burning gasoline, like any kind of fossil fuel, makes carbon dioxide, which makes global warming. Since 2017, less gasoline powered cars are being made,[2][3] and some places will not allow gasoline-powered cars in future, like Amsterdam in 2030.[4]

The cleanest cars are electric vehicles. They are usually plugged into a power outlet or a charging station and store electricity in a battery at the bottom of the car. The electricity then drives an electric motor, which turns the wheels. Some electric cars have 2 motors: one at the front, and one at the back. A few have 4 motors (one for each wheel).[5]

Some cars burn diesel fuel, which is used in big trucks and buses, and a few use wood gas. In some countries, such as Brazil and Sweden, a mixture of ethanol and gasoline, called "gasohol" in Brazil and "E85" in Sweden, is used as automobile fuel. Other fuels include propane, natural gas, compressed air, and ethanol (which comes from plants). There are cars designed to run on more than one type of fuel — these are called "flex-fuel" and are rare.

A few cars generate electricity from hydrogen fuel cells (like the Honda Clarity). As of 2019, most of the hydrogen that people use comes from burning fossil fuels, but scientists and engineers are trying to make hydrogen from renewable energy a lot cheaper and easier to use.

Some cars even use solar cells for their electricity, but they are not very practical. There is a competition every year where people try to design a car that can last the longest and go the farthest on solar energy alone.

There is also a type of car that uses both an engine and an electric motor. This is called a hybrid electric vehicle; an example is the Toyota Prius.

All cars have brakes which work by friction to stop the car quickly in an emergency or stop it rolling when parked. Electric cars also have regenerative brakes, which slow the car by turning the energy in its movement back into electricity, like an electric motor working the opposite way. So regenerative means the electricity is generated again.

The earliest recorded automobiles were actually steam engines attached to wagons in the late 18th century.  The steam engines were heavy, making these wagons slow and hard to control. Better and faster steam cars became common late in the 19th century.

Some cars in the early 20th century were powered by electricity. They were slow and heavy and went out of use until the idea came back later in the century.

The internal combustion engine changed the way many automobiles were powered. The engine used either gasoline, diesel, or kerosene to work. When the fuel is exploded in a cylinder it pushes the piston down and turns the wheels.

Although many people tried to make a good car that would work and sell well, people say that Karl Benz invented the modern automobile. He used a four-stroke type of internal combustion engine to power his Benz Patent-Motorwagen in 1886. He began to make many cars in a factory and sell them in Germany in 1888.

In North America, the first modern car was made by brothers Charles and J. Frank Duryea in Springfield, Massachusetts. The Duryea brothers' car also won the first-ever car race in 1895, competing against cars made by Benz. The race was in Chicago, Illinois, and 53 miles long. The Duryeas then began making the first automobiles for everyday use in 1896. That year, they made 13 cars by hand in Springfield, Massachusetts.

Benz may have invented the first modern car, and the Duryeas the first car to be sold, but Henry Ford sold the most cars to the most people. In 1910 he began making and selling his Model T, which was a huge success. Many people could afford this car, not just the rich, because Ford used mass production. This meant he made many Model Ts in a short time in a factory. People say that the Model T is the car that "put America on wheels". The Model T was the most popular car of the time because it was cheap but it was still a good quality car that ordinary people could own.

Since then, many different kinds of cars have been designed and built, from minivans to sports cars. In the 1950s, the United States made and used more cars than all the rest of the world. Fifty years later, China became the largest maker and user of cars.

Cars are faster than walking or riding a bike if you are going a long way. They can carry more than one person and a large amount of luggage. Depending on local public transport quality, they can also be faster and far more convenient than using buses, bicycles or trains, and can often go where public transport cannot. 4-wheel drive "off road" vehicles are particularly good at reaching places difficult for other wheeled transport due to bad roads or harsh terrain. However, they cost more and burn more fuel, and there are many places even they cannot go.

Most cars enclose people and cargo in a closed compartment with a roof, doors and windows, thus giving protection from weather. Modern cars give further protection in case of collisions, as they have added safety features such as seat belts, airbags, crumple zones and side-impact protection that would be expensive or impossible on two-wheeled or light 3-wheeled vehicles, or most buses.

With regular check ups and service, cars can last a very long time. In some countries like Australia, you have to get your car checked by authorised mechanics regularly by law to confirm that your car is safe to drive. You can go to a car mechanic to get your car checked or have a mobile mechanic come to you to repair your car.

Buying and running a car needs a lot of money, especially for newer good-quality cars.  There are things to pay for — the car itself, fuel, parts (for example, tyres), maintenance, repairs, insurance to cover the cost of crashes or theft, parking charges, and toll roads and any taxes or licensing fees charged by the government.

When cars crash, they can become damaged and hurt people, and the life of a person is more important than keeping a car from damage.  When too many cars try to go the same way, traffic congestion slows them all. Cars can cause air pollution if too many are used in a small area like a city, and the combined pollution of the world's cars is partly to blame for climate change. Many places where people live close together have public transportation such as buses, trains, trams and subways. These can help people go more quickly and cheaply than by car when traffic jams are a problem. Some of these problems can be made smaller, for example by carpooling, which is putting many people together in one car.

Traffic congestion and accidents can be dangerous to other road users, for example people riding bicycles or walking, especially in an old town built when cars were few.  Some 20th century towns are designed for cars as the main transport.  This can cause other problems, such as even more pollution and traffic, as few, if any, people walk. Communities are divided and separated by big roads.  Pedestrians are in danger where there are too few foot bridges, small road bridges or other special crossings.