Are performance ratings of the cpu true? If not what should i overclock to?

I have a lenovo pc, it has 2ghz. Now when i go to system requirement labs it says it is performance rated at 3.6. What does this mean? Can i play games that require 3ghz because of this with no problems? If not i would overclock, i don't know whats the safest i should overclock to either.

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