An automobile is a four-wheeled passenger vehicle that uses an internal combustion engine to power its wheels. It usually runs on gasoline, diesel fuel or kerosene. The automotive industry was dominated by the United States until the late 20th century when it was surpassed by Japan.

Modern automobiles are complex technical systems with a variety of functional design subsystems, some that have evolved from breakthroughs in existing technologies and others resulting from new ones such as electronic computers and high-strength plastics and alloys. There are three main types of automobiles: passenger cars, commercial vehicles (trucks, buses) and special vehicles (fire engines, ambulances and infantry fighting vehicles).

Automobiles allow people to travel long distances quickly without the need for a guide. They also enable people to move more items and carry larger loads than is possible with other wheeled transport. They can travel over rough terrain that other wheeled transport cannot, and they can also go to places where public transportation is not available.

Karl Benz, a German engineer, invented the first automobile in 1885. The modern automobile was designed with a four-stroke internal combustion engine powered by petroleum (gasoline) sparked in the cylinders with spark plugs. The resulting explosions drive the pistons down and turn the wheels.

The car opened up the world for many people. It allowed them to move from place to place, which created a lot of jobs in hotels and motels, restaurants, service stations, gas pumps and the like. People could also work in several locations and have homes in different areas, if they wanted to. The automobile also facilitated leisure activities, such as traveling to visit relatives, shopping and visiting sports events and amusement parks.

As the automobile became more popular, people also needed to have parts and services for their vehicles, and these industries grew. This helped make the United States a wealthy nation. The automobile also enabled women to take on roles that were previously reserved for men, such as driving or serving as chauffeurs for their owners.

However, there are negative aspects to the automobile. Automobiles pollute the environment with air pollution, and their use can drain dwindling oil supplies. People can also be injured or killed in accidents involving automobiles. Traffic congestion can slow down many cars. And some people find it annoying to wait for the next bus or train.

In the postwar era, engineering was often subordinated to the questionable aesthetics of nonfunctional styling and a desire for higher unit profits. The result was that by the mid-1960s American-made cars had twenty-four defects per unit, many of them safety-related. The era of the gas-guzzling road cruiser was ended by federal standards on safety, emissions and fuel efficiency, as well as the rising price of gasoline.