Land-and-groove recording
Writing data on both the grooves and the raised lands between them, nearly doubling track density on recordable optical discs.
Pressed CDs and DVDs store data in a single spiral of pits. Recordable formats such as DVD-RAM and some magneto-optical discs instead write on both the groove and the land (the ridge) between grooves, packing twice as many tracks. Note that "land" here isn't the same as in pit-and-land readback, where the land is merely the flat between pits. The head has to track both levels.