Short answers, pulled from the story.
Rhodium was discovered in 1803 by William Hyde Wollaston. He isolated it from crude platinum ore, presumed to have come from South America, through a series of chemical precipitation steps, and named it after the Greek word for rose because of the rose-red color produced by one of its chlorine compounds.
Rhodium's primary use is in three-way catalytic converters for automobiles. In 2012-81% of the 30,000 kilograms of rhodium consumed worldwide, specifically 24,300 kilograms, went into this application. The metal's role is to reduce nitrogen oxide emissions in vehicle exhaust.
Rhodium is one of the rarest elements in Earth's crust, present at less than one part per billion. Annual global production fluctuates around only 30 tonnes, with 75% coming from South Africa. Its price ranged from less than US$700 per troy ounce in 2016 to nearly US$30,000 per troy ounce in 2021.
Rhodium flashing is the process of electroplating a thin layer of rhodium onto white gold or platinum jewelry to give it a bright, reflective white surface at the point of sale. The layer gradually wears away with use. Sterling silver is also rhodium-plated to protect against tarnish.
Volvo introduced the three-way catalytic converter in 1976, which was the first major automotive converter to use rhodium. Earlier catalytic converters used only platinum or palladium. The three-way design required rhodium specifically to reduce nitrogen oxides in exhaust, and this application has since driven roughly 80% of global rhodium demand.
In 1979, the Guinness Book of World Records gave Paul McCartney a rhodium-plated disc to recognize him as history's all-time best-selling songwriter and recording artist. The choice of rhodium was intended to signify a level of achievement beyond what gold or platinum could represent.