Automobiles (also called cars) are motor vehicles used for travel on land. They usually have four wheels and an internal combustion engine, fueled most commonly by gasoline (also known as petroleum products). Modern automobiles are generally designed for passenger travel with the ability to carry two to six people and small amounts of cargo. The automobile is a versatile and useful transportation device that has revolutionized human society.

The automobile was first developed in the late 1800s, but it was not until Henry Ford perfected the assembly line that it became affordable to most Americans. The advent of the automobile caused an economic boom that transformed cities and stimulated the growth of many new industries, including steel fabrication, vulcanized rubber, and road construction. It also brought many changes to social life, as it gave families more freedom to shop and travel, and made it easier for couples to spend time together without needing a babysitter.

Automobiles have a complicated system of parts that must be designed to interact with each other, and it is not easy to find the right balance between power, comfort, safety, and cost. Choosing between front-wheel drive, rear-wheel drive, independent suspension, and other features will affect the way an automobile handles and performs. The fuel type, which can be either gasoline or diesel, will also affect the performance and economy of a car.

In general, the automobile is powered by an internal combustion engine that burns a fuel to produce energy to propel the vehicle forward. The engine can run on a variety of fuels, but the most common is gasoline. The energy produced by the engine is transferred to the wheels via a transmission system that allows the car to go at different speeds.

There are other systems in the automobile that must be designed to work together, including the steering and braking system, cooling and lubrication system, electrical system, and chassis. The chassis consists of the frame, which supports the other systems, and the wheels and tires. The wheels are typically manufactured from steel, although alloys of aluminum and magnesium are sometimes used. The tires are made of natural or synthetic rubber, or, in some cases, plastic.

As a result of the complex interaction between the various systems of an automobile, most modern cars have become very sophisticated. They are used in all kinds of activities, from family trips and shopping to business and commercial deliveries. An automobile can be driven on highways, city streets, or in rural areas. Most cars are powered by gasoline, but some use electric power from a battery. These vehicles are referred to as hybrids. Some models can operate in electric-only mode at low speeds, while the gasoline engine takes over for cruising and to recharge the battery. The hybrid design makes automobiles more environmentally friendly than traditional gasoline-powered cars.