Electromagnetic spectrum is the range of frequency (spectrum) of electromagnetic radiation and wavelength and photonic energy respectively.
Electromagnetic spectrum includes electromagnetic waves with frequencies below one hertz to more than 1025 hertz, which correspond to wavelengths of thousands of kilometers to the size of the nucleus. These frequency bands are divided into separate bands, and electromagnetic waves in each band are called by different names. Starting from the end of the low frequency spectrum (long wave) are: radio waves, microwaves, infrared rays, visible light, ultraviolet, X-rays, and gamma rays at the high frequency ends (short waves). Electromagnetic waves in each of these bands have different properties, e.g. How they are produced, how they interact with the material, and how they are used in practice. Long wavelength is the size of the universe itself, while short wavelength is believed to be close to the Planck length. High gamma rays, X-rays and ultraviolet rays are classified as ionizing radiation because their photons have enough energy to ionize atoms, which causes chemical reactions.
In most of the bands above, a technique called spectroscopy can be used to physically separate the waves at different frequencies to get a spectrum showing the frequency of the component. Spectroscopy is used to study the interaction of electromagnetic waves with matter. Other technological applications are explained under electromagnetic radiation.