Yeah the frequency. AMD has a build in method of reducing clock speed at idle to save power, I can't remember what it's called. If you run a game or something else cpu intensive and then check cpuz you should see the frequency at it's default value.
Mhm. Like Intel's Speedstep.
You can turn it off if you want, but there's not much reason to. Some people think having it off makes for more stable overclocking, but I think that's a thing of the past.