The EM spectrum is the way scientist measure the amplitude and frequency of light. A wavelength is the distance between the tops of two waves. The the shorter distance between wavelengths the stronger the energy. Then tall and wide waves have less energy and the short and close ones have the most.
Amplitude is the height of waves and it determines the amount of energy.
The distance between to waves aka the "frequency" of when they appear and it determines the color of light waves with low being red and high being violet