Our brain is made up of two halves, a left brain a right brain. There's a big fold that goes from front to back in our brain, essentially dividing it into two distinct and separate parts. Well, almost separate. They are connected to each other by a thick cable of nerves at the base of each brain.
This sole link between the two giant processors is called the corpus collosum. Think of it as an Ethernet cable or network connection between two incredibly fast and immensely powerful computer processors, each running different programs from the same input. That is how it works scientifically.
Let's identify those "left brain" types who are very analytical and orderly. We likewise certainly know of the artistic, unpredictability and creativity of "right brain" types. But each of us draws upon specific sides of our brain for a variety of daily functions, depending on such things as our age, education and life experiences.
Thus the choices of which brain is in control of which situations is what forges our personalities and determines our character.