Microwaves have wavelengths approximately in the range 200 μm to 30 cm (corresponding to a frequency range of 1 - 1500 GHz). However, the boundaries between far infrared light, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
A microwave oven uses a magnetron microwave generator to produce microwaves at a frequency of approximately 2.4 GHz for the purpose of cooking food. Microwaves cook food by causing water molecules to vibrate - heating them, and the rest of the food, up. Since organic life is made up primarily of water food is easily cooked by this method. A maser is a device similar to a laser, except that it works at microwave frequencies. Microwaves are also used in satellite transmissions because this frequency passes easily through the earths atmosphere less interference than higher wavelengths.