What is a variant and where do you use it?

If you want to run a report program with same selections at regular intervals (for
example, for monthly sales statistics), you would not want to enter the same values each
time. So, ABAP/4 offers you a possibility to combine the desired values for all these
selections in one selection set. You can create as many different selection sets as you
like for each report program and they remain assigned only to the report program in
question. Such a selection set is called a variant.

Using Variants Online
Using Variants in Background Processing

Online, starting a report via variant saves the user work,minimizes input errors. In
background processing, a variant is the only possibility you have to pass values for the
selections.

To fill certain selections with values that change according to the application, you use a
variant, which takes the variable values from Table TVARV.