TCS stands for temperature for safety food.
TCS food is temperature control to prevent the growth of microorganisms able to grow in food, by adapting to pH, humidity and the presence of proteins and carbohydrates.
After TCS food has reached 165°F in a microwave oven the food should be kept at this temperature for at least two minutes so all parts of the food (even on the inside) should have this minimal temperature of 165°F.