7types of electromagnetic waves from lowest to highest frequency

radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

Explanation:

Electromagnetic waves are the waves which are created as the result of the electrical waves which are perpendicular to each other and also perpendicular to the direction of propagation.

Electromagnetic spectrum is range of the frequencies and their respective wavelengths of the various type of the electromagnetic radiation.

In order of the increasing frequency and the photon energy and the decreasing wavelength the spectrum are:  

radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.

vapour or gas assuming atmospheriv pressure