Language Reference wrote:FILLER
A data item that is not explicitly referred to in a program. The keyword FILLER is optional. If specified, FILLER must be the first word following the level-number.
The keyword FILLER can be used with a conditional variable if explicit reference is never made to the conditional variable but only to values that it can assume. FILLER cannot be used with a condition-name.
In a MOVE CORRESPONDING statement or in an ADD CORRESPONDING or SUBTRACT CORRESPONDING statement, FILLER
items are ignored. In an INITIALIZE statement, elementary FILLER items are ignored.
If data-name-1 or the FILLER clause is omitted, the data item being described is treated as though FILLER had been specified. [emphases added]
If you are a beginner, try to understand all of this. Try to explain to us the part in italics
. I think it would be a good exercise in "how to understand what the manual is saying", which, to me, is always vital.