From Bushin SOFTWARE:
Parking Status is a small Windows gadget that shows and changes CPU's core parking status. Core parking is a new feature that Microsoft introduced in Windows 7 and Windows Server 2008 R2. Depending on the resource use of the operating system it may park one or multiple cores of a multi-core cpu to reduce the computer's power consumption and thermal emissions. Once operations require more processing power, the parked cores are activated again to assist in the tasks.
Desktop users may benefit from it on their utility bill. For some multi-core processors, core parking is not enabled by default, and if you want to enable the feature you will be hard pressed to find any tools or information that allows you to do that. Users with AMD processors on the other hand may experience less than optimal processing powers while core parking is enabled on their system. You may remember that this was an issue some time ago. Microsoft has released a hotfix for AMD users that disables core parking on the system.