Okay, bear with me, I am not a neuroscientist. So my understanding of these networks is less about their scientific nuances than about their potential meaning in the Whole Mind.
Let's start with the Default Network 
. This network is our original, or primordial network. This is the network that allows us to perceive danger and to respond for survival.
As such, this network is closely tied to our emotions. For survival, a primary emotion is fear. But we are filled with a plethora of other emotions, all of which appear to be processed by this network in order to make meaning of them. These emotions derive for our experiences as human beings.
These are the thoughts that largely fill our minds. Worries, desires, fears that ignite a continual stream of thoughts. These are thoughts that we react to.
These reactive thoughts can also overwhelm our ability to analyze and think logically, the role of the Executive Network . It appears that this executive network is key to developing meaning through sequential logic, that ability harnessed for mathematic, analytic, and scientific thought.
Then there is the Salience Network a network that has only recently been identified. This network allows us to create meaning from contrasts. What does it mean to be a red dot on a white background? This network is likely key to understanding the Hacking experience.
Through this process we synthesize contradictions into new, higher meanings, a process that can be called Dialectical Synthesis.
One could argue that we are at our highest potential and can enter an empowered Flow State when all three networks are illuminated and engaged.