Microwave radiation is form of electromagnetic radiation with wavelengths ranging from one meter to one millimeter, which gives its frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm). This means that its wavelength is a lot larger than that of visible light that you are using to read this page, but shorter than, say, radio waves that power your TV or radio.

Microwave radiation is commonly found in Microwave ovens, hence the name(!), which use a frequency near 2.45 GHz (12 cm) to heat up water molecules in your food.