Automobiles are four-wheeled passenger vehicles that are usually powered by an internal combustion engine using a volatile fuel. Modern automobiles are complex technical systems, with thousands of component parts. Each of these has specific design functions. An automobile consists of an engine, transmission, chassis, bodywork, control systems and electrical equipment. The engine can be gasoline (carburetor internal combustion), diesel, electric, or gas turbine powered. The power from the engine is transferred to the wheels via a gearbox or transmission. The automobile can also use an alternate source of power such as wind, solar, or hydroelectricity.

Automobiles have revolutionized society by enabling families to live beyond the confines of the urban area where they work or school, and to travel widely and conveniently. As the world population grows, so too does the need for personal transportation. Today, an estimated 1.4 billion automobiles are in operation worldwide, and most of these are cars. Of this total, more than three trillion miles or five trillion kilometres are driven each year.

The car has become one of the most important inventions in human history. It has transformed the way we live and the way we communicate. It is used as a mode of public and private transportation, as well as a means of recreation. In addition to the comforts of the cabin, which can include air conditioning, heater, and radio, a variety of features are available for passengers, including cushioned seats, steering wheel, dashboard, and rearview mirror.

An automobile can go faster and farther than pedestrians, bicycles or even trains (steam, diesel, or light rail), and can also travel to places where no other mode of transport can go. However, there are also disadvantages to owning a car. Automobiles are prone to accidents due to their size and speed, and they can be costly to repair or maintain. They are also a major contributor to environmental pollution and drain of dwindling world oil supplies.

The first true automobile was built by Nicolas-Joseph Cugnot of France in 1769. Later, manufacturers developed steam-powered automobiles, which were heavy and moved slowly. By the late 1800s and early 1900s, automobiles had come to dominate European and American roads, thanks to innovations like the Model T invented by Henry Ford and mass production techniques that lowered prices so that middle-class Americans could afford them.

The development of automobiles continued in leaps and bounds after 1920, but by the 1950s the industry had reached near saturation. New technology was largely limited to improved versions of existing components and systems, such as the electric self-starter (invented by Charles Kettering for General Motors in 1910), closed all-steel bodies, and hydraulic brakes. Moreover, the profit margins that the big American automakers enjoyed based on high unit sales were offset by the cost of new technological developments.