A corporation is a legal entity that is separate and distinct from its owners. Corporations enjoy most of the rights and responsibilities that individuals possess: they can enter contracts, loan and borrow money, sue and be sued, hire employees, own assets, and pay taxes. Corporations are legal persons, on the same level as citizens before the law. Corporations are immortal, enjoying perpetual succession. Human citizens are not.
Corporations control (and contribute) a large section of a national economy. In the United States nearly 70% of the country's GDP is derived from large companies in the corporate sector. Developing economies, like India, have smaller corporate sectors accounting for only 12-14% of the national GDP.