Your organization may have multiple divisions corresponding to multiple lines of business with different requirements for EPM solutions. Your IT department may also want to have a separate Project Server instance configured for testing and troubleshooting purposes. In these cases you need to set up and configure multiple Project Server sites.
You can use the Edit Site utility to quickly create a Project Server–hosted deployment and to edit the properties for existing hosted sites. A hosted deployment is typically a large installation of Project Server 2003 that hosts Project Server site collections for different departments or divisions within the organization.