Correlation studies and measures the direction and intensity of relationship among variables. If the two variables X and Y move in the same direction, i.e., with an increase in one variable, the other variable also increases or with the fall in one variable, the other variable also falls, the correlation is said to be positive. E.g. When the income rises, consumption also rises. There is a positive correlation between them.
Whereas if the two variables X and Y move in the opposite direction, i.e., with the increase in one variable, the other variable falls or with the fall in one variable, the other variable rises, the correlation is said to be "Negative correlation”.
E.g. When the price of a commodity rises, its demand falls. There is a negative correlation between them.