Radiation is a type of energy transfer in which energy is transferred by a source that travels through space or a vacuum.
Energy transfer by radiation is at the speed of light.
Radiation consists of electric and magnetic fields or it is an electromagnetic wave.
This energy has an electric field and a magnetic field associated with it and has wave-like properties. You could also call radiation “electromagnetic waves”.
Hence, radiation is a type of energy transfer in which energy is transferred by a source that travels through space or a vacuum.