The plasma is the fourth state found after the material 3 state (solid, liquid, gaseous). It consists of ionized conductive gases, including six typical particles, namely electrons, positive ions, negative ions, excited atoms or molecules, ground atoms or molecules, and photons.

In fact, plasma is a quasi-neutral gas composed of a large number of positive and negative charged particles and neutral particles, and exhibits collective behavior, that is, highly ionized gas. Whether it is partial ionization or complete ionization, the total number of negative charges is equal to the total number of positive charges, so it is called plasma.