Short answers, pulled from the story.
Michael Faraday proposed that matter existed in forms beyond the known solid, liquid, and gas states during his lectures titled On Radiant Matter. He described this new state as existing far beyond vaporization just as vaporization exists above fluidity.
Sir William Crookes presented findings to the British Association for the Advancement of Science on Friday, the 22nd of August 1879. He used the term radiant matter to honor Faraday's earlier speculations while presenting laboratory observations.
Plasma consists of unbound positive ions and negative electrons moving freely yet generating collective electromagnetic fields. Individual particles experience forces from distant charges rather than simple binary collisions found in neutral gases.
More than 99 percent of all ordinary matter in the visible universe exists as plasma. Stars function as pure balls of plasma heated by nuclear fusion processes.
Generating artificial plasma requires applying electric current across a dielectric gas until electrical breakdown occurs. Electrons bound to atoms detach during collisions creating ions and additional free electrons in a Townsend avalanche process that multiplies charged particles millions-fold after twenty successive collision sets.