James Clerk Maxwell , an English scientist, developed a scientific theory to explain electromagnetic waves . He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves. Neither an electrical field, nor a magnetic field will go anywhere by themselves. But, Maxwell discovered that a changing magnetic field will induce a changing electric field and vice-versa.
An electromagnetic wave exists when the changing magnetic field causes a changing electric field, which then causes another changing magnetic field, and so on forever. Unlike a static field, a wave cannot exist unless it is moving. Once created, an electromagnetic wave will continue on forever unless it is absorbed by matter. 
Heinrich Hertz , a German physicist, applied Maxwell's theories to the production and reception of radio waves. In fact, the unit of frequency of a radio wave is named the hertz, in honor of Heinrich Hertz.
Hertz proved the existence of radio waves in the late 1880s. He used two rods to serve as a receiver, a spark gap as the receiving antennae, because it generates an electric spark, a simple receiver of looped wire and two pairs of polished bross knobs; two of those are connected to an induction coil. Where the waves were picked up, a spark would jump. Hertz showed in his experiments that these signals possessed all of the properties of electromagnetic waves.
With this oscillator, Hertz solved two problems. First, timing Maxwell's waves. He had demonstrated, in the concrete, what Maxwell had only theorized - that the velocity of radio waves was equal to the velocity of light! Second, Hertz found out how to make the electric and magnetic fields detach themselves from wires and go free as Maxwell's waves. 
Electromagnetic waves, called EM waves, are a special type of waves that can travel without a medium. Unlike sound waves and water waves, electromagnetic waves don't need a fluid, or a solid, or even air to help them travel from one place to another. The creation of all electromagnetic waves begins with a charged particle . This charged particle creates an electric field. When it accelerates as part of an oscillatory motion, the charged particle creates oscillations, in its electric field, and also produces a magnetic field. So, electromagnetic waves are named for the fact that they have both an electric and a magnetic component. Just like regular transverse waves, the oscillations of electromagnetic waves are perpendicular to the direction of the wave's travel. The electric component oscillates in one plane, while the magnetic component oscillates in a different plane and they are perpendicular. In a vacuum, electromagnetic waves always travel at the same speed - the speed of light. While time passes, the electric field E and the magnetic field B change according to the harmonic motion law: they increase together to a maximum value, then, still together, they nullify themselves and they arrive at the same time, to their minimum values. This motion continues in a regulary period called T, and its frecuency is inversally proportional to the period, so the formula is f=1/T. As for all periodic waves, the equation that relates wavelength and frequency for electromagnetic waves is: λν=c where λ is the wavelength (measured in meter), ν is the frequency (measured in hertz) and c is the speed of light ( measured in meter/second). While in Italian, the equation is λf=ν where λ is the wavelength (measured in meter), f is the frequency (measured in hertz) and ν is the speed of light ( measured in meter/second). 