Thanks for the link. That is the answer to my question. It is still a bit confusing but I think I'd have to read up on some physics to understand what still confuses me.
They don't say what type of liquid that's inside the tubes but under a vacuum it boils at lower temperatures, it boils and the vapor travels away from the heat source, taking it into the cooling fin area that the fan or fans are moving air over the cooling fins, cooling down the vapor.
The vapor cooled goes back to a liquid state and uses the capillary action to return to the heat source, and cycles all over again, so it's constantly in a flowing process of heating and cooling the liquid inside the heat pipes.
Since the liquid is sealed inside the tubes it cannot just evaporate off, like if you were boiling water on a stove, so the preset level of liquid for each heat sink, stays the same.
It's all pretty simple to wrap your brain around except for the capillary action, returning the cooled liquid back to the heat source, that's quite remarkable.