3-2-1 refers to a method of cooking ribs that involves placing them in the pellet grill/smoker at a relatively low setting, typically 225 degrees for 3 hours. This is the smoking stage for the ribs.

The second stage is the ribs are wrapped up in foil with a liquid/sauce added in so they can braise for 2 hours.

The final stage, for the last hour of cooking, is to get the ribs out of the foil and get them on the grates with some BBQ sauce to develop a little bark before they are ready to eat.

3-2-1 ribs have become a very popular method to cook ribs on a pellet grill/smoker. However, there are detractors and those who think there are better methods.