Critical = important factors that affect food safety
Control = the cook has control over conditions and actions
Point = step in the food prep process
My impression of a critical control point is that the person in charge (in your kitchen and pit area this is you) is required to review all steps of the food delivery, storage, prep, cooking/holding, and serving process and determine any steps in this process that would allow the food to be compromised, as in exposed to any contaminants or unsafe temperatures for too long a period of time. Once the critical control points have been identified, you need to develop a plan to minimize the likelyhood of bad things happening.
For the BBQ enthusiast that would include your shopping. If you purchase raw meat at Super Wally and intend to transport it to your home, the meat temperature needs to be maintained at a certain point during transportation. Put simply, you can't throw a brisket in the back of your pickup and make 6 stops on the way home. Use a cooler. From the time of purchase to storing in your refrigerator at home could be considered a critical control point.
Take that brisket out of the refrigerator and put it on the counter for injection and or rubbing. Because the raw meat is not in a controlled environment (cryovac in the fridge) and out on your counter at room temp, this would be a critical control point. You do have control over the time that it sits on your counter. A desirable plan would be to minimize this time.
Another, and related example is pit temperature and holding food in the "danger zone". We should all know that most raw meats, with obvious exceptions for rare beef, and in my opinion chicken in particular, need to spend as little time possible at temps between 40* and 140*. This would be a critical control point. You do have control over that pit temperature.
Many more examples, and if you look at it, it's all just common sense.
This was just a ramble on my part. Good subject to discuss for sure and I look forward to others input.