In physics and chemistry, a plasma is typically an ionized gas. Plasma is considered to be a distinct state of matter, apart from gases, because of its unique properties. Ionized refers to presence of one or more free electrons, which are not bound to an atom or molecule. The free electric charges make the plasma electrically conductive so that it responds strongly to electromagnetic fields.
Plasma typically takes the form of neutral gas-like clouds (e.g. stars) or charged ion beams, but may also include dust and grains (called dusty plasmas). They are typically formed by heating and ionizing a gas, stripping electrons away from atoms, thereby enabling the positive and negative charges to move more freely.
There are many other applications of plasmas with enormous economic importance. For example, plasmas are widely used in the semiconductor industry covering more than 50 % processing of manufacturing Integrated-Circuit (IC) Chips. Cheap modern microchips could not be made without plasma aided manufacturing. Plasmas are also used for applying high performance coatings for engineering and medical applications.
Left picture shows an example of a plasma in argon gas with 2.45 GHz microwave excitation. Plasmas are used for not only processing semiconductor materials but also nano-, bio- and enviromental applications.