A provider is a system resource capable of making a shadow copy. Microsoft provides a standard provider with Windows Server 2003/2008
Use the vssadmin list providers command to display available providers
vssadmin add shadowstorage Enables VSS for a volume
vssadmin create shadow Creates a shadow copy for a volume
vssadmin delete shadows Deletes shadow copies for a volume
vssadmin delete shadowstorage Disables VSS for a volume
vssadmin list providers List VSS providers
vssadmin list shadows List Shadow copies
vssadmin list shadowstorage List storage enabled for VSS
vssadmin list volumes List volumes enabled for VSS
vssadmin list writers List VSS writers
vssadmin resize shadowstorage Resize the space set aside for VSS
Example
vssadmin delete shadows /For=C: /Oldest /Quiet
The command line options provide the same functionality as the GUI and in some instances additional information not provided by the GUI, such as details on providers and writers