Digital Command Control (DCC) uses digital technology to allow operation of several trains at the same time. For example, shunting operations can be carried out while a train is running on the main line. A microprocessor signal decoder must be fitted into each locomotive, which can then be individually controlled, regardless of the speed and direction of other trains. DCC provides power to the track constantly, so train lighting and sound is maintained unless the track section is switched off, as happens with standard points. Best results are therefore obtained when all tracks are made permanently live and connected in parallel.
DCC systems and devices (eg locomotive decoders) are required to meet a set of standards for connectivity and inter-operability maintained by the NMRA, the National Model Railroaders Association in the USA. You can select devices like decoders from manufacturers that comply with NRMA standards and be confident they will work with other makes.