Correlation is a statistical measure that describes the relationship between two variables. When two variables are correlated, it means that when one variable changes, the other tends to change in a specific direction. This relationship can be positive, where both variables increase together, or negative, where one variable increases while the other decreases. Correlation does not imply causation, meaning that just because two variables are correlated, it does not mean that one causes the other to change. For example, the correlation between ice cream sales and temperature may indicate that both increase during summer, but it does not mean that one causes the other.