From Dr. Peter Drucker:
A business enterprise has two basic functions: marketing and innovation
If we want to know what a business is, we have to start with its purpose. And the purpose must lie outside the business itself. In fact, it must lie in society, since a business enterprise is an organ of society. There is only one valid definition of business purpose: to create a customer. The customer is a foundation of a business and keeps it in existence. The customer alone gives employment. And it is to supply the customer that society entrusts wealth-producing resources to the business enterprise.
Because it is the purpose to create a customer, any business enterprise has two – and only two – basic functions: marketing and innovation. These are the entrepreneurial functions. Marketing is the distinguishing, the unique function of the business.