Microwaving cooks foods by using microwaves that have been generated when electrical energy is converted into long wave, electromagnetic energy, i.e. microwaves. As microwaves contact the food, the energy is absorbed by the food, which causes the water molecules in it to vibrate so generating heat via friction. Microwave radiation penetrates the food readily and is much quicker than infrared radiation at heating food, because microwaves have a much higher frequency than infrared radiation and its frequency of c. 2.5 GHz is readily absorbed by larger organic molecules in foods..
Microwaving is best used to heat (or reheat) foods rapidly - microwaves are good for reheating ready-made meals, but while convenient for defrosting they leave a residual rotten taste to the defrosted meats.
However, heating via microwaves: does not brown food as well as convection or barbecuing for example, tends to dry out meats and vegetables like potatoes, so is often not a decent substitute for conventional cooking methods; however, microwaves that are combined with convection ovens can overcome this by switching it on to brown the food.