Correlation is commonly classified into negative and positive correlation.
The correlation is said to be positive when the variables move together in the same direction. When the income rises, consumption also rises. When income falls, consumption also falls. For instance, sale of ice-cream and temperature move in the same direction.
The correlation is negative when they move in opposite directions. When the price of apples falls its demand increases. When the prices rise its demand decreases. When you spend more time in studying, chances of your failing decline. These are instances of negative correlation. The variables move in opposite direction.