WMI Filters

WMI Filters are a useful tool when using Group Policy.
WMI Filters allow you to target specific classes of objects.

For examply, say you create a policy that you want to only apply to Domain Controllers

SELECT * FROM Win32_OperatingSystem WHERE ProductType = 2

Or more importantly you have a policy that you want to exclude Domain Controllers

SELECT * FROM Win32_OperatingSystem WHERE ProductType <> 2

Or you want to target Laptops

SELECT * FROM Win32_Battery WHERE (BatteryStatus <> 0)

This WMI Filter users WMI to discover the workstations 'BatteryStatus', If the battery status is not 0 (a battery is present) then consider the device a laptop.

References

http://technet.microsoft.com/en-us/library/cc947846%28v=ws.10%29.aspx