Short answers, pulled from the story.
James Christy discovered Charon on the 22nd of June 1978 while examining photographic plates at the United States Naval Observatory. This discovery occurred nearly half a century after Pluto itself was found in 1930.
The International Astronomical Union officially named Nix and Hydra on the 21st of June 2006, Kerberos emerged from search efforts and was announced on the 20th of July 2011, and Styx was discovered during a hunt for potential hazards facing the New Horizons spacecraft and announced on the 7th of July 2012. These objects received provisional designations S/2005 P 1 and S/2005 P 2 before receiving official names later that year.
Charon measures about half the diameter of Pluto yet holds nearly one eighth of its total mass. This massive ratio places the system barycenter outside either body at approximately 878 kilometers above Pluto's surface.
Scientists suspect the entire satellite system formed from debris after a massive collision similar to the impact thought to have created Earth's Moon because high angular momenta within the system can only be explained by such a violent scenario rather than captured Kuiper Belt objects. Nearly circular orbits suggest these bodies formed during the collision event itself.
The next period of mutual events involving Charon begins in October 2103 and peaks during 2110 before ending in January 2117. Only the hemisphere facing Charon experiences solar eclipses because tidal locking keeps that side fixed toward the companion.