Hi Kumar,
Please check out the documentation below, which explains the reason for these dimensions and includes a use case.
https://experienceleague.adobe.com/docs/campaign-classic/using/automating-with-workflows/introductio...
The reason for these functions is to allow for the excluded target schema to match up with the destination. This could mean that you want the data to be reconciled based on an identifier (say primary key), or a specified join, or by changing the dimension entirely (see doc here for an explanation of the change dimension logic)