Capitalism is an economic system that emphasizes private ownership of the means of production or a privately controlled economy. In a capitalist society, you have a free market and companies live by the profit motive. They exist to make money and maximize the wealth of their shareholders, whether they have one shareholder or thousands. Prices, production, and the distribution of goods are determined by competition in a free market.
A capitalist system is also called a market economy. There is a limited regulatory framework. Legislation is supposed to define and enforce the basic rules of the free market. The government does provide some public goods and services as well as support.
Under a this system, small businesses drive the economy. They provide most of the jobs - up to 70-80%. Large corporations provide most of the profit, but small businesses are the job creators.