This video gives a DCC introduction and demonstrates the differences between DC and DCC
The DCC Demonstration is intended to show the many advantages of digital command control over direct current
Digital model railway control systems are an alternative to control a layout and simplify the wiring and add more flexibility in operations. A number of control systems are available to operate locomotives on model railways. Analog systems where the speed and the direction of a train is controlled by adjusting the voltage on the track are still popular while they have recently given way to control systems based on computer technology.
a useful introduction to DCC technology