Subsites can be created beneath top-level sites. They can contain the same elements that top-level sites can contain (document libraries, lists, Web Parts, and so on) but typically are designed to provide information to a subset of the users of the top-level site that is related to the top-level site's functionality. For example, a top-level site might be created for a department, such as Engineering, and subsites created below it for divisions of the department, such as Electrical Engineering and Mechanical Engineering. Alternatively, a top-level site might be created for the Sales department, and subsites created for key clients or projects.
It is important for the organization to think through the design of the Windows SharePoint Services site collections and SharePoint Portal Server 2003 environment to ensure that the right top-level sites and subsites are created for the user community. There needs to be a good combination of features and functionality so that top-level sites are available for the appropriate departments, committees, or groups and that the appropriate subsites are created, while ensuring that the SharePoint environment is navigable and manageable.
The structure of site collections is important for several additional reasons. The administrator of the top-level site can control settings for the top-level site and any subsites beneath it. Also, if the top-level site is moved or deleted, the subsites will be too. The subsites can also inherit rights from the top-level site, use the site groups available in the top-level site, and access Web Parts stored in the top-level site. The administrator of a subsite, however, can control settings for only that subsite, and the administrator of the next subsite can control settings only for that subsite.