Radio frequencies (RF) form a fragment of the entire electromagnetic spectrum. It is generally considered that radio frequencies are found between 10 kHz and 300 GHz. 10 kHz is considered to be the lower end of the electromagnetic spectrum. Above 300 GHz infrared begins. Electromagnetic energy travels as waves that move at the speed of light (300 000km/s), normally in a straight line. Electromagnetic waves have two components, electric and magnetic. These are at right angles to each other. Unlike sound waves, electromagnetic waves do not need a medium through which to pass. Hence radio transmissions to and from deep space are possible.
At high power, radio waves can be dangerous and can carry a lot of energy, hence the expression "RF energy". Amateur radio operators are usually not subject to those radiations unless they are standing close to antenna equipment or have poorly installed equipment, see RF in the shack.