Electromagnetic radiation is the type of energy that propagates through a vacuum. Different portions of the electromagnetic spectrum are known by different names, such as light, heat and radio waves, but are all part of the same phenomenon.
Electromagnetic radiation travels in waves through empty space but is also simultaneously propagated by particles such as electrons and photons in a phenomenon called wave and particle duality. The different types of electromagnetic radiation are determined by wavelength, which also corresponds to energy. Radio waves have long wavelengths, measured in meters, and have relatively low energy. Light waves have short wavelengths, measured in nanometers, and much higher relative energy.