Plasma is by far the most common form of matter. Plasma in the stars makes up over 99% of the visible universe and perhaps most of which is not visible.
On Earth we live upon an island of matter that which we are all familiar. The different states of matter generally found on Earth are solid, liquid, and gas. We have learned to live, work, and play, using all the familiar states of matter. In 1879, Sir William Crookes, an English physicist, identified a fourth state of matter, now called plasma.
In 1929 the word "PLASMA" was first applied to an ionized gas in by Dr. Irving Langmuir, an American chemist and physicist.
Conditions at the Sun's core (approximately the inner 25% of its radius) are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the center of the core the Sun's density is more than 150 times that of water.
Plasma temperatures and densities range from the relatively cool and tenuous (like the aurora borealis) to very hot and dense (like the central core of our Sun). Ordinary solids, liquids, and gasses are both electrically neutral and too cool or dense to be in a plasma state.
Aurora is Latin for "dawn", it is a glow in a planet's ionosphere caused by the interaction between the planet's magnetic field and charged particles from the Sun.
The "Northern Lights"; caused by the interaction between the solar wind, the Earth's magnetic field and the upper atmosphere. A similar effect happens in the southern hemisphere where it is known as the aurora australis.
Plasma consists of a collection of free-moving electrons and ions-atoms that have lost electrons. Energy is needed to strip electrons from atoms to make plasma. Plasma energy can be formed by several origins such as thermal, electrical (resistance heating), or light (ultraviolet light or intense visible light from a laser). A plasma arc forms where the electrical potential flows either from negative to positive, or positive to negative through a highly ionized gas. With insufficient sustaining power, plasmas generally recombine into neutral gas. Aside from the Sun and aurora borealis as examples of plasma energy, other forms of plasma manifest themselves in the form of lightning and static electricity.
On Earth, we find plasma energy useful by harnessing it to work for us. We use it for the many forms of lighting (neon, fluorescent, high-pressure sodium, metal halide, etc.) it is used for welding, the steel industry, ceramics, electronics industry, and now for the waste industry.