It will work like any other Drupal site using Domain Access. You can choose to share various database tables and mark various pieces of content per domain. The best use case I can think of is a t-shirt supplier that has a unique store brand for "upscale modern" and "fringe skaterz" -- but doesn't want to maintain two websites. You could theoretically use domain access for this scenario. Often, I've found the blood sweat and tears of doing a successful domain access project is not worth the time or feature set you were after.

If you are after multi-store functionality ala "etsy.com" then you should read and chime in here: http://drupal.org/node/990204

Josh