An "If-Then Statement" is a logical expression used to show a cause-and-effect relationship. It consists of two parts: the "if" part, which presents a condition, and the "then" part, which describes the outcome that follows if the condition is met. For example, "If it rains, then the ground will be wet." These statements are commonly used in programming, mathematics, and everyday reasoning. They help in making decisions based on specific criteria. For instance, in computer programming, an If-Then Statement can control the flow of a program by executing certain actions only when specific conditions are true.