Sharepoint object model

In Sharepoint Object model there are two Important namespaces.

The Microsoft.Office.Server namespace is the root namespace of all Office Server objects and Microsoft.SharePoint is the root namespace for all WSS objects.

The Chart Below illustrates some of the key classes contained in each of these namespaces, as well as to which functional area they belong.

Document Libraries (Microsoft.SharePoint)
SPDocumentLibrary , SPPictureLibrary

Business Data Catalog (Microsoft.Office.Server.ApplicationRegistry.Administration)
EntityCollection , ApplicationRegistry

Features (Microsoft.SharePoint)
SPFeatureDefinition, SPFeatureScope, SPElementDefinition, SPFeature, SPFeatureProperty

Sites (Microsoft.SharePoint)
SPSite, SPSiteAdministration, SPSiteCollection, SPWeb

Meetings (Microsoft.SharePoint.Meetings)
SPMeeting, MtgUtility

User Profiles (Microsoft.Office.Server.UserProfiles)
UserProfile, UserProfileManager

Solutions (Microsoft.SharePoint.Administration)
SPsolution, SPFeatureReceiver, SPSolutionCollection

Lists (Microsoft.SharePoint)
SPList, SPListItem, SPListItemCollection

Note:
* To use the SharePoint API, your code must reside on one of the machines in a SharePoint
application server farm. Your code can still work with other sites in the farm from any
other site in the farm, but you cannot, for example, work with the SharePoint API from a
machine on which MOSS or WSS is not installed.

* The only practical way to consume SharePoint data and functionality from a remote client is to use the SharePoint web services.

* The object model is not designed to support Remoting.

* To add a reference to a Sharepoint API, Right-click the project(in VS) and select Add Reference. Click the Browse tab and select the
following directory:
C:\program files\common files\microsoft shared\web server extensions\12\isapi