Short answers, pulled from the story.
Astronomer James Christy discovered Charon on the 22nd of June 1978 while examining photographic plates at the United States Naval Observatory Flagstaff Station. The International Astronomical Union announced this discovery to the world on the 7th of July 1978.
James Christy initially suggested naming the moon Oz but colleagues proposed Persephone before he insisted on Charon. The IAU officially adopted the name in late 1985 and announced it on the 3rd of January 1986.
Charon and Pluto orbit each other every 6.387 days within the outer solar system with a mutual tidal locking that keeps the same face toward one another. This unique dynamic places the barycenter outside Pluto itself because their masses are comparable enough to create a dwarf double planet system.
Simulation work published in 2005 by Robin Canup suggests Charon formed from a collision around 4.5 billion years ago involving a large Kuiper belt object striking Pluto. This impact scenario explains why both bodies share very similar densities despite differences in surface composition.
Charon has no significant atmosphere because its gravity cannot hold gases against solar winds which remove them faster than they can accumulate. Any gas reaching Charon is held closely against the surface making amounts negligible compared to Pluto's total atmosphere.
Images showing Pluto and Charon resolved into separate disks were taken for the first time by the Hubble Space Telescope in the 1990s. The New Horizons spacecraft became the only mission to visit and study Charon during July 2015 closest approach creating the best animation available at that date.