WSS 3.0 Lists Web Service
The Windows SharePoint Services Web services provided by the Microsoft.SharePoint.SoapServer namespace includes methods that provide Microsoft .NET Framework developers with object models for creating solutions that work with Windows SharePoint Services remotely from a client or custom application. They are defined through the server-side object model of the Microsoft.SharePoint assembly, and their design is optimized to reduce the number of roundtrips transacted between client computer and server.
Most Web services are provided through the /_vti_bin virtual directory, which maps to the \\Program Files\Common Files\Microsoft Shared\web Server extensions\12\ISAPI physical directory. The Administration Web service is provided through the /_vti_adm virtual directory, which maps to \\Program Files\Common Files\Microsoft Shared\web Server extensions\12\ ADMISAPI physical directory.