Need to understand Default implementation in Enhancement spot(Multiple use)

Hi Abapers,

We are having some issue in Enhancement spot (Default Implementation).

This is Multiple use BADI,initially we have created one implementation and enabled as default and moved to Quality system. After that we have created another implementation as non-default.

Default implementation got deactivated while activating Non-default Implementaion and while triggering program default implementation not yet triggered.

Need to know purpose of Default Implementation.

Also when do we need to make Default Implementation in enhancement spot .

Thanks,

Rajesh