By the appearance there is very little different, both grades are created with the same image and the finish can be very similar. The real difference is in the backing of the material.HPL or high pressure laminate has a plastic backing and is the more durble of the two as well as having a high degree of water resistance due to the pre-consumer recycled plastic backing but this also make the material much harder giving it a superior scratch resistance

LPL or low pressure laminate is the same paper or pictures that is just not applied to a plastic backing. The lack of plastic backing in this application makes the material a More susceptible to damage by water or scratching.