A Local variable is local to the formula it is declared in. If you have the same
variable name in another formula, it is a different variable.
A Global Variable can be used in several formulas and it is the same data. We will
demonstrate this global variable shortly.
A Shared Variable can be used in formulas to exchange data between a main report
and a subreport. Shared Variables must be evaluated WhilePrintingRecords. We
will demonstrate this in the Subreport exercises in tomorrows course.