Hi,
Since you posted the question in the eBay section of the Forum, I'm guessing the domain was obtained for that purpose.
When the domain name is assigned to your Auctiva eBay Gallery store, what you list on eBay will appear in the gallery store and store window (same as always). The domain name simply provides a more distinctive method to advertise your eBay sales rather than the store.auctiva.com/mystoreID method (like the 2 in my sig).
Danno