Directions - How Google Maps gets you to your destination

In this day and age, we are now relying on mapping applications on our phones to get us to our destination more and more.  Google Maps and Apple Maps are great.  They find a route to where you are going fast and predict the time so much better than even a couple of years ago.  But, how do they do that?  How do they predict how long it takes and how do they know about traffic.  Better yet, which one is better.  Mark and Jeff explore this topic