In driver-based planning, financial lines are calculated from the underlying activity. Revenue might be units times price, labor cost might be headcount times loaded salary, and a farm's input cost might be acres times cost per acre. Changing a driver updates every number that depends on it.
Drivers make plans easier to understand and update. A conversation about whether volume will be 10 percent lower is more productive than one about a revenue cell. The trade-off is that drivers need to be chosen carefully. Too many make the model fragile, while too few hide the real causes of change.