DAB -
Digital Audio Broadcasting is currently the
prevalent standard in many countries for
Digital Radio.
DAB allows for "crystal-clear" sound quality (although not quite CD quality), a more robust signal which is less prone to interference, better usage of frequencies to allow for more stations to be broadcast, and carriage of data information - such as text information displayed on tuners, and web pages to be displayed on computers.
amnesiac's Digital Radio writeup has more information on the type of compression used.