3-2-1 is for Spare Ribs
2-2-1 is for Baby Back Ribs
3-2-1 method is put the ribs in a 225 degree smoker for 3 hours after the 3 hours foil them tight and back in for 2 hours then take them back out of the foil and back into the smoker for 1 hour.
2-2-1 is the same method only change in the times
Many people will spritz/mop the ribs after the first 1-1.5 hours each 45 minutes - 1 hour. Many also add a little of the spritz/mop to the foil before sealing it. If you are going to baste with sauce many do that in the last hour