Digital Command Control (DCC) is a means of running a number of locomotives on the same track at the same time.  This will add a new dimension to your model train layout.  Imagine seeing 2 goods trains and a passenger service on the layout at the same time.

DCC is not hard to setup, as most locomotives can be purchased DCC ready.  This is something that you will need to think about when purchasing your locomotives.  Existing layouts and locomotives can also be converted to DCC.  This will add another dimension to your enjoyment of this already fun hobby.