IDiscoveryService Web Service
A single Microsoft Dynamics CRM installation can host multiple organizations on multiple servers. Therefore, it is important to specify which organization you want to access. The IDiscoveryService Web service returns a list of organizations that the specified user belongs to and the URL endpoint address for each organization. For more information about the IDiscoveryService Web service, see Discover the URL for Your Organization with IDiscoveryService Web Service and IDiscoveryService.
IOrganizationService Web Service
The primary Web service for accessing data and metadata in Microsoft Dynamics CRM 2011 is the IOrganizationService Web service. For more information about the IOrganizationService Web service, see Use the IOrganizationService Web Service to Read and Write Data or Metadata and IOrganizationService.
Add the Microsoft Dynamics CRM 2011 Assemblies to Your Project
Most of the time you will choose to use the SDK assemblies in your development projects. Using the assemblies is the recommended developer scenario for Microsoft Dynamics CRM 2011 and Microsoft Dynamics CRM Online. These assemblies are in the SDK\Bin folder, along with the corresponding Visual Studio IntelliSense XML files. For more information about the assemblies, their contents and usage, see Assemblies Included in the Microsoft Dynamics CRM SDK.
Add the Service Reference to Your Project
You may have a development scenario where you want to include the service reference in your project rather than using the assemblies. To find the correct service references for your organization, see Download the Endpoints Using the Dynamics CRM Developer Resources Page.