Member function Usage with example please

[Pramod]

Hi All

I am working on a dimensional model where there is a custom group I have to create. Say I have to create a logical hierarchy of zone for 3 region(A,B,C)

I did it this way

member(aggregate(currentmeasure within set filter( region,caption(region) in (A,B,C))),Zone,ZONE)


But my doubt is what is the use of this ZONE member in my report.
How else can I use this member.