What do you mean by electromagnetic spectrum?

There are many types of electromagnetic radiations such as cosmic rays, gamma rays, X-rays, ultraviolet, visible light, infrared light, microwaves and radio waves. All electromagnetic waves have the same speed (3 X 10⁸ ms^-1). However, different types of radiations differ from one another in their wavelengths and therefore in frequency. The arrangement of different types of electromagnetic radiations in the order of increasing wavelengths or decreasing frequencies is known as electromagnetic spectrum. Different regions of the electromagnetic spectrum are identified by different names. Complete electromagnetic spectrum is as shown.
The visible light in the presence of which our eye can see certain radiations is having wavelengths between 380 nm to 760 nm. Different colours in the visible light correspond to radiations of different wavelengths.
Out of the various colours in the visible range. Violet colour corresponds to radiation of minimum wavelength (380 nm) while the red colour corresponds to radiation of maximum wavelength (760 nm)