Automobiles are self-propelled vehicles used for transporting people. Having four to eight wheels, they are powered by an internal combustion engine or an electric motor and can be driven on roads. Various definitions have emerged for the term, but most agree that it refers to wheeled motor vehicles that are designed to carry passengers and a small amount of cargo. Unlike trucks (or omnibuses or coaches), automobiles are primarily built for passenger transportation. Several branches of engineering are involved in the manufacture and development of automotive vehicles.

Invented and perfected in Europe toward the end of the 1800s, automobiles became a key component of modern life in the United States in the early 1900s. The automobile revolutionized industries, technology, and everyday life. Among the changes, it increased the personal freedom of Americans and created new jobs in dozens of spin-off industries that provided services for drivers like motels, hotels, restaurants, recreation and amusement, and fuel. In addition, it gave rise to new government requirements like seat belts and highway rules. It also brought harm to the environment with exhaust from gas-burning cars and took over undeveloped land for building roads.

As the automobile grew in popularity, it helped to create suburban neighborhoods and to expand urban centers. Until recently, almost every American family owned one or more of them, and most commuters travel by car. It is believed that the modern automobile has surpassed the horse as the dominant mode of transport, although there are still many other modes of transportation.

Modern automobiles use gasoline, although diesel engines that run on petroleum-based fuel are common for heavy vehicles like buses and trucks and for a few high-end passenger vehicles. The power of the engine is transmitted to the front or rear axles through a transmission system. Depending on the model, the engine is either air-cooled or water-cooled. The latter is more efficient, but requires a radiator.

Besides the standard passenger cars, there are special automobiles for goods carrier and for special usage. These vehicles include bus, mini-bus, truck, pick-up van, and trailer. They are usually operated by professional drivers. There are also some automobiles with computerized systems that greatly aid or even replace human driving. This type of automobile is called semiautonomous or autonomous vehicle. Currently there is much focus on developing such vehicles, which would be capable of taking control of the vehicle in certain situations and at different speeds. Whether such autos are safe remains to be seen. However, the development of these systems may change the future of the automobile industry. The Age of the Automobile is melding into a new age of electronic media and robotics. These new technologies will have a major effect on the way people travel and on the types of automobiles they will use. Hopefully, these technological advances will allow for safer and more environmentally friendly ways of getting around. They may also lead to more efficient vehicles that will reduce traffic congestion and emissions, which are causing problems around the world.