It has been reiterated a few times what the importance of a thermometer is when cooking meats. Once you stick the probe inside of a particular food, it will display the internal temperature of said food.
But, as many of you know, this can vary depending on where you insert the probe. For the best results, always place it in the center of the thickest piece of meat. This will be the coldest portion of it, and if this is cooked, then the rest will be.
However, it can get a bit tricky, depending on the size of the sensor. Thankfully, most digital thermometers will have tiny sensors on the tip to eliminate the guesswork. But, with a large sensor, the thermostat will almost take the average temperature of each portion that is in contact with the sensor.