Profit, simplistically, is what is earned above and beyond the costs of the business.

Role of profit
Profit fulfills the function of putting a premium on successful innovation, therefore incenting entrepreneurs to innovate. (Schumpeter, 1942)

• Profit fulfills an economic function in an evolving economy, one that changes with innovation. ""... 'profit' is a genuine cost, the cost of staying in business, the cost of a future in which nothing is predictable except that today's profitable business will become tomorrow's white elephant."" (Drucker, Peter F., 1983, Schumpeter and Keynes, Forbes 23 May, 124-128)
• ""Profit is like oxygen, food, water, and blood for the body; they are not the point of life, but without them, there is no life."" (Collins, 1994)