Short answers, pulled from the story.
Charon was discovered by James Christy, an astronomer at the United States Naval Observatory, on the 22nd of June 1978. He identified it by noticing a periodic elongation in photographic plates of Pluto taken at the Naval Observatory Flagstaff Station. The International Astronomical Union formally announced the discovery on the 7th of July 1978.
James Christy chose the name Charon as a scientific-sounding version of his wife Charlene's nickname, Char. He later found that Charon is also the ferryman of the dead in Greek mythology, closely linked to the god Pluto. The IAU officially adopted the name in late 1985, with the announcement made on the 3rd of January 1986.
Charon has a mean radius of 606 km, making its diameter just over half that of Pluto. It holds roughly 12.2% of Pluto's mass, a ratio far larger than any other moon relative to its parent body in the Solar System.
The reddish north polar region of Charon, formally called Neverland Regio, is composed of tholins, which are organic compounds formed when nitrogen, methane, and carbon monoxide that escaped from Pluto's atmosphere freeze at temperatures as low as -258 degrees Celsius and are then chemically altered by solar radiation. When the pole warms seasonally to around -213 degrees Celsius, the volatile ices sublimate away, leaving only the tholins behind.
New Horizons is the only spacecraft to have visited and studied Charon. It made its closest approach to the Pluto system in July 2015, passing within 27,000 km of Charon. Charon's discoverer James Christy and the children of Pluto's discoverer Clyde Tombaugh were present at the Johns Hopkins Applied Physics Laboratory for the event.
The question remains open. Because Charon has 12.2% of Pluto's mass, the barycenter of the Pluto-Charon system lies outside Pluto itself, meaning neither body truly orbits the other. A 2006 draft IAU proposal would have classified Charon as a planet on those grounds, but the final definition did not resolve the status of planetary satellites. The IAU currently lists Charon as a satellite of Pluto but has acknowledged that a dwarf planet reclassification may be considered in the future.