If you're asking this to make sure if you should buy it, then think no more!
Dual core CPU's are the best choice right now. Just buy it and your comp will run like a champ!
But if you need a further explanation. It's like two separate CPU's. Imagine that your motherboard has two CPU's and you can only use each to do one task. In a way yes, you have the 6.0GHz because if you're burning a disc you use one core (3.0GHz) then if you start another demanding task, the other core will start going (which is total 6.0GHz). BUT, if you are only doing one thing, it will not perform using the whole 6.0GHz.
Hope I didn't confuse you.
