Expected value is a fundamental concept in probability and statistics that represents the average outcome of a random variable over numerous trials. It is calculated by multiplying each possible outcome by its probability and summing these products. This concept is crucial in various fields, including finance, game theory, and machine learning, as it helps in making informed decisions under uncertainty. For instance, in gambling, understanding expected value can guide players on whether a game is worth playing. Overall, expected value provides a powerful tool for evaluating risks and rewards in uncertain situations.