Marginalism is an economic theory that focuses on the importance of small changes in decision-making. It emphasizes how individuals and businesses make choices based on the additional benefits or costs associated with consuming or producing one more unit of a good or service. This approach helps explain how prices are determined in markets and how resources are allocated efficiently. The concept of marginal utility, introduced by economists like Carl Menger and William Stanley Jevons, is central to marginalism. It suggests that the value of a good decreases as more of it is consumed, influencing consumer behavior and market dynamics.