Remember, in the old days, Pork Crackling was the hot/warm crackling you got from a nice joint of roast pork.
Pork Scratchings were a cold snack of rind & fat, found in those little bags that you bought from behind the bar at the pub.
But things have changed. Pork Scratchings are still the same. But Pork Crackling can now refer to the traditional crackling as mentioned above plus a ‘new’ type of double-cooked, slightly lighter version of traditional pork scratchings.