SharePoint comes with the list of proprietary controls that you can use in your applications. Controls are splitted between:
- User Controls that locates in 12-hive\TEMPLATE\CONTROLTEMPLATES folder - 58 controls
- Web Controls in Microsoft.SharePoint.WebControls namespace - about 212 controls (Microsoft.SharePoint.Dll, Microsoft.SharePoint.ApplicationPages.Administration.dll)
Knowing these controls plays a vital role on the way of becoming a good SharePoint developer.