An arrangement of all wavelengths of electromagnetic radiation is called the spectrum. The plural is spectra. Below is a graphic showing the electromagnetic spectrum.  Note that for light, the wavelength tells you the color. The unit of wavelength in the figure is the nanometer, which is a billionth of a meter.  Visible light has a wavelength range of 400-700 nm.  Keep in mind that the divisions are a human invention. There are no real breaks between the different types of radiation.