Behavioral finance blends psychology, economics, and finance to explain how investors make decisions and how these choices impact markets. It challenges traditional theories by recognizing that investors aren't always rational, helping to explain market anomalies like bubbles and crashes. Key concepts include prospect theory, mental accounting, and heuristics. These ideas shed light on cognitive biases and emotional factors that influence financial decision-making, offering practical applications for investors, advisors, and policymakers to improve market efficiency.