Theory of the firm is a way of thinking about businesses and companies. It helps us understand the way businesses think and make decisions. Basically, the theory of the firm says that businesses should think about the costs and benefits of their decisions before they make them. That means that businesses should try to make decisions that will help them make more money or save more money in the long run. For example, if a business is considering buying new machines to help them make their products faster, they should think about how much money the machines will cost and how much money the machines will help the business make in the long run. In this way, businesses can make better decisions.