The Seasons Graph tool is designed to graphically highlight the changes in seasons.
By choosing the drop-down box in the Data section, all aspects of the data are available to display. You can view either individual Products, Customers or Salespeople, or the respective categories for each of these aspects.
The trendline options provide the ability to plot an average line against the data to envisage how the data would have been "smoothed", or potentially could occur, in a future period.
Please keep in mind that trendlines are an approximation at best. In Salesmatrix datasets, they will display the best results with full sets of data (i.e. 12 periods of data in two years). With small sets of data and disparate amounts (especially varying negatives and positive values) the resulting trendline may not be usable.