The beginnings of any object model exploration should start with a basic understanding of what you're working with. Windows SharePoint Services delivers to developers an object model comprising 30 public namespaces in 10 assemblies. Taken from the Windows SharePoint Services SDK (at http://msdn2.microsoft.com/en-us/library/ms453225.aspx), the following table contains a subset of this list of public namespaces, which assembly files they're each contained in, and a short description of what each namespace offers to developers. For the full list, please refer back to the WSS SDK documentation.
|Microsoft.SharePoint||Microsoft.SharePoint (in Microsoft.SharePoint.dll)||Provides types and members for working with a top-level site and its subsites or lists|
|Microsoft.SharePoint.Administration||Microsoft.SharePoint (in Microsoft.SharePoint.dll)||Provides administrative types and members for managing a Microsoft Windows SharePoint Services deployment|
|Microsoft.SharePoint.Deployment||Microsoft.SharePoint (in Microsoft.SharePoint.dll)||Provides types and members for importing and exporting content between Windows SharePoint Services web sites|
|Microsoft.SharePoint.Meetings||Microsoft.SharePoint (in Microsoft.SharePoint.dll)||Provides types and members that can be used to customize Meeting Workspace sites|
|Microsoft.SharePoint.MobileControls||Microsoft.SharePoint (in Microsoft.SharePoint.dll)||Provides server controls for rendering the mobile forms and view pages used in SharePoint ...|