Plasma is a state of matter that is often called "the fourth state of matter," along with solid, liquid, and gas). It is essentially an electrified gas, and it only exists when there is enough energy in the system to strip atoms apart. In a plasma, many of the electrons wander around freely among the nuclei of the atoms, and a significant number of electrons have such high energy levels that no nucleus can hold them. This results in a medium of unbound positive and negative particles that is highly electrically conductive, and the overall charge of a plasma is roughly zero). Although the particles in a plasma are unbound, they are not "free" in the sense of not experiencing forces. Moving charged particles generate electric currents, and any movement of a charged plasma particle affects and is affected by the fields created by the other charges).

Plasmas can appear in nature in various forms and locations, including artificially produced, terrestrial, and space and astrophysical plasmas). They are by far the most common phase of ordinary matter in the universe, both by mass and by volume). Because of their sizable temperature and density ranges, plasmas find applications in many fields of research, technology, and industry, including electric lamps, lasers, medical devices, energy converters, water purifiers, and flat-panel video displays).

In summary, plasma is a state of matter that is essentially an electrified gas, and it is highly electrically conductive. It is the most common phase of ordinary matter in the universe and has many applications in various fields of research, technology, and industry.