Think about this, the theme is moving rocks from the truck to your yard. Each worker moves at different rate (speed) than other workers)
Cache = barrels
GHZ = How fast your men can work
Core = path
Now, you got a single core. You got 2 men working to pore rocks into your yard. Each one is sent out at a time because there is only one path. Now lets say you send 2 at the same time in the same path. Great faster but now the 1 person to go has to wait for the second one to come there so he can come back to get more rocks.
Now, you got a dual core. You got 4 men working to pore rocks into your yard. 4 is sent out at a time because there is 2 paths BUT!!! both paths are connected together (Core Communication). So the first man to finsh, switches path so the other works don't have to wait for him to turn around and pass them to get more rocks because he can find a path that's open
Now you got a quad core. You got 8 men working to pore rocks into your yard. 8 is sent out at a time because there is 4 paths. However now you got 4 paths connected to each other. So the the 1st man to finsh waits untill a path is free than goes back.