Multiple Stores functionality allows you to power number of stores or websites within a single Magento installation. It is useful if you are going to sell products on different domains sharing the same admin panel and to track your sales and customers without having to login to the admin area of each website. There a number of different ways to enable the Multi-Store Functionality. Here is how to enable multiple Magento webstore login.
Below is a method which shows how to run two websites under the same admin area but it will also be useful, if you are going to run the sites under two different domains as well.