Simply speaking, electromagnetic waves are the waves of electromagnetic radiation (or EMR for short). As a matter of fact, transformation of electric field generates magnetic field and vice versa, we name the waves generated by the interaction of electronic and magnetic field electromagnetic waves.

Similar to light and heat, electromagnetic wave is certain form of energy and may transmit by air or through conducting materials. The times that electromagnetic waves transform per second present their frequency. With higher frequency, electromagnetic waves may transmit even without any intermediate conductors and they perform the character of radiation which may be divided into three different style: ionizing radiation, non-ionizing radiation with heat effect and non-ionizing radiation without heat effect.

Actually, anything that emits energy inevitably emits electromagnetic waves. Hence there exist invisible electromagnetic waves everywhere around us in our daily lives; mobile phone electromagnetic wave is one typical sample that we come across every day.