Plasma by definition is a highly ionized gas that usually occurs at high temperatures that conducts electricity and is affected by a magnetic field. But did know that plasma is the most common state of matter(if you don't count dark matter which hasn't been proven yet) Plasma is what makes up suns as well as lightning bolts and some regions of the earth's upper atmosphere. A plasma is composed of positive charged ion and free electrons but they're separate despite the attraction for each other. If they were to combine, the would turn back into a ordinary gas. In order to overcome the attraction of the charges for each other, there ether has to be large amounts of energy which is usually heat that keeps the particles moving too fast to combine or there is so much space between the particle that they can't combine which means they have low density. Here on Earth we use plasma to cut metals while on the sun, the plasma form of hydrogen combines to form helium and releases massive amounts of energy.