why do u specify i_structure_name in FM 'REUSE_ALV_FIELDCATALOG_MERGE'

Hi,

my query is :

plz expalin abt the feilds i structurename and

I_INTERNAL_TABNAME

in FM 'REUSE_ALV_FIELDCATALOG_MERGE'

and when these 2 fields are used??

Iam getting confused with this?

plz explain me clearly???

regards

mallik