This feature is currently only available in the Philippines, where all Philippines based TackThis shops are aggregated into a marketplace called www.takatack.com
Once you have added a Shop Alias in your Shop Settings, your shop will automatically be assigned a unique marketplace shop URL based on your Shop Alias.
So if you have set your Shop Alias as awesomeshop, then visitors will be able to access your shop via both:
Note that having your shop listed on the marketplace is not the same as getting featured. Drop firstname.lastname@example.org a note if you want your shop to be featured!
Having a unique marketplace URL is necessary for those who wish to setup their own Custom Domain.