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 as well. This relationship can be positive, where both variables increase or decrease together, or negative, where one variable increases while the other decreases. It is important to note that correlation does not imply causation. Just because two variables are correlated does not mean that one causes the other to change. For example, the correlation between ice cream sales and temperature may exist, but it does not mean that buying ice cream causes the temperature to rise.