You may notice that some of our cooking instructions call for removing items from the heat before they reach their target temperature. That's because of carry-over cooking, which is basically the idea that foods will continue to "cook" even after being removed from the heat. You may have also heard of "resting," which is essentially the 3-5 minutes that you let the cooked food rest after cooking in order to reach its final temperature, and the reason why food doesn't get cold immediately after you finish cooking it.
This occurs because the outer edges of the item you are cooking is hotter than the center because that area is closer to the heat source. This is why the outside of a burger that is in contact with the pan gets a nice sear, while the inside can be cooked to a rosy pink.
When you check the temperature of your food with a thermometer, you do so in the center of the item because that will be the coolest part, and for food safety reasons you want to make sure the entire item is cooked to the proper temp. But the key to extra juicy meats is to just barely reach this temperature, otherwise your food can overcook very quickly. That's because smaller items (like burgers or chicken breasts) tend to rise in temperature around 5°F after removing them from the heat, and larger items (like a pork tenderloin) as much as 10°F. So pulling these items off the heat 5-10°F before a thermometer in the center of the item reaches that temperature and allowing it to rest 3-5 minutes (depending on the size of the item) is that chef trick that will make your dinner guests ask you for your cooking secret. Make sure to rest the meat on a cutting board or plate, since the hot pan or baking sheet will cook the meat even further since it is still very hot.
Of course, you'll want to check the temperature after the resting period to make sure you hit the mark, and if not you can quickly throw it back over the heat to get it to the proper temperature.