An electric charge creates an electric field. The electric field is how a charge transfers its force to other electric charges.
A moving electric charge creates a magnetic field which is how it can transfer magnetic forces.
A vibrating charge like an electron oscillating in an antenna creates both an electric field and a magnetic field simultaneously. The combined fields produced by the vibrating charge is called an electromagnetic field.
The electromagnetic field produced by the charge radiates (or propagates) away from the charge in the form of energy waves. These energy waves are composed of the electric field and the magnetic field oscillating as they move away from the charge. The waves produced in this way are called electromagnetic waves. Electromagnetic waves are forms of electric and magnetic energy which can be transferred through space without a medium.
The frequency of the energy waves that are created by the oscillating charges depends on how fast the charges are oscillating. If they oscilate quickly they make high frequency electromagnetic waves, if they oscillate slowly they make low frequency electromagnetic waves. The range of all the possible frequencies of electromagnetic waves that can be made by oscillating charges is called the electromagnetic spectrum. Human beings are able to detect certain frequencies of the electromagnetic spectrum. We call that range of frequencies the "visible light spectrum" and include all of the frequencies of light from dark red through dark purple (ROY G BIV).