A "random walk" is a mathematical concept that describes a path consisting of a series of random steps. Imagine a person starting at a point and flipping a coin to decide whether to move left or right. Each flip determines the next step, creating a sequence of movements that can lead to various outcomes. This concept is used in various fields, including physics, economics, and biology. In finance, random walks are often used to model stock prices, suggesting that future price movements are unpredictable and follow a random pattern. This idea is closely related to the Efficient Market Hypothesis, which posits that all available information is already reflected in stock prices, making it difficult to predict future movements based on past trends.