One of the useful features in Magento is the ability to create multiple stores/websites that share the same Magento installation. This allows multiple store fronts to share a common code base and backend, making administration a lot easier. Stores can share customer base, product catalog and settings based on how you choose to configure your sites.
This tutorial will go through the steps of setting up multiple stores in Magento, and how to configure a domain for each store.
https://www.properhost.com/support/kb/30/How-To-Setup-Magento-With-Multiple-Stores-And-Domains
