DCC Throttles add flexibility to run more closely to where the trains are. Either on your own or with friends DCC Throttles allow for multiple trains to be run at the same time!
A throttle (or Cab if referring the analog) is a way to control the locomotives, and other aspects of the layout (turnouts, animation, lighted passenger cars, etc).
There are many types of throttles available, with some features overlapping various types. The range of throttle types ranges from stationary, tethered (throttle connected via wires), memory walk-around, and tetherless - no wires - uses infrared and radio. Each of these can be anything from full-featured to simple basic throttles, but not necessarily with all the other options. Lets break this down.