They refer to time amounts when cooking ribs. For instance 3-2-1 means 3 hours on the smoker, 2 hours wrapped in foil braising in liquid (apple juice usually) then 1 hour uncovered again to firm up. There are variations, the 2-2-1 you mentioned is used alot for spare ribs. That first number is not always set in stone though, it's just a guide line. You know the ribs are ready to wrap when the meat pulls away from the bone about a 1/4 inch. Also during that last hour some folks like to glaze the ribs at that point. Hope this helps.
3-2-1 is too rough a time frame to produce prime product but it does give you an idea of the technique. Here is a small write I did for the WBBQA site:
Competition Ribs technique
This technique can be used for pork spares or Baby Backs cooking time will very based on which ribs you cook.
I will start with spares. They will be trimmed St Louis style. Two hours before they are to go on the pit I will rub front and back.
The pit temps I use are 250 to 275 with your choice of wood for smoke.
The first portion of the cook will last aprox 3 hours, during this part of the cook I am looking for color, it is that nice carmel color and you will see the meat to just start to pull back on the bone. Once the right color is achieved I will move into the second part of the cook.
In this stage I take H/D foil spread some honey, hit with a little cayenne pepper and a little hot pepper sauce. I place the ribs face down in the mixture and repeat the the process on the back side. Add some fruit juice (apple or pineapple is a good choice), seal the foil and place back on the pit. This part of the cook will last 45 min to an hour on average. What I look for is more pull back of the meat on the bone and the ribs become tender. You can use toothpick, sliding into the meat between the bones, if it feels like it is going into warm butter they are ready to remove from the foil.
The rack go back on the cooker and apply glaze. The glaze should be set in 15 to 30 min based on pit temp.
This just one technique there are others, this is more of a process than a recipe. You can use any good pork rub and a suace that is in balance with the rub.
I look for a flavor print that when eaten you will first get the sweetness of the sauce, then the tang also from the sauce with spice and a little heat come through at the end from the rub. I look for a rub that is on the spicy side (heat wise) and use a sauce that I sweeten up with honey.
This technique is to produce ribs that come clean off the bone but not fall off the bone. Should you want fall off the bone ribs then you can increase the time in foil.
I found an idea from Good Eats w/ Alton Brown. Although he did the entire cooking process in the oven, his braising liquid made some sense. I start w/ about a cup or so of brown sugar (depending on how much meat I'm cooking), throw in some garlic and a few pinches of salt, spill in some chili powder (sometimes I make up my own), add a splash or two of vinegar, a double splash of white wine, a few splashes of worcestershire, a big serving of honey, and a big ol' splash of apple juice. (and maybe an extra spice or two, depending on whether the spice cabinet is open and something catches my eye.)
Use this in the foil during the two-hour braising process. When you take them off, poke a hole in the foil and drain all the liquid into a sauce pan. Place the ribs on the smoker for the last hour. At the same time, simmer the juices for about 15 minutes to reduce it to a glaze. Then glaze the ribs and let them cook for the rest of the last hour.