Looking at data over a number of years and finding patterns, you can use this information to extrapolate future patterns. A trend means that the same series of events is happening over and over. For example, if there is a trend of constant sales each year with a decrease of sales in winter that is offset by an increase in the summer, a person might extrapolate this to predict that sales will continue to be low in the winter. A store manager might use this information to offer additional products in the winter to help hedge against a drop in sales that time of year. However, forecasting isn't done quickly by just looking at a graph. Forecasters may translate the patterns of a graph into a formula to better predict what will happen in the future. They also may use spreadsheet software, which typically comes with built-in trend forecasting tools.