Short answers, pulled from the story.
Pluto was discovered by Clyde Tombaugh on the 18th of February 1930, at Lowell Observatory in Flagstaff, Arizona. He identified it by comparing photographic plates taken on January 23 and 29, 1930, using a blink comparator to spot the object's movement against background stars. News of the discovery was telegraphed to the Harvard College Observatory on the 13th of March 1930.
The International Astronomical Union redefined the term "planet" in August 2006 to require that a body orbit the Sun, be rounded by its own gravity, and have cleared the neighborhood around its orbit. Pluto meets the first two conditions but not the third: its mass is only 0.07 times the combined mass of all other objects in its orbital zone, compared to Earth, whose mass is 1.7 million times the remaining mass in its orbit. The IAU designated Pluto a dwarf planet and assigned it the minor-planet number 134340.
The name was first suggested by Venetia Burney (1918-2009), an eleven-year-old schoolgirl in Oxford, England, who was interested in classical mythology. She proposed it to her grandfather Falconer Madan on the morning he read the discovery news to the family at breakfast; Madan passed the suggestion to astronomy professor Herbert Hall Turner, who cabled it to Lowell Observatory on the 16th of March 1930. The name was published officially on the 1st of May 1930.
Pluto orbits the Sun at an average distance of 39.5 AU, ranging between 30 and 49 AU due to its elliptical orbit. At that distance, sunlight takes 5.5 hours to arrive. One complete Plutonian orbit takes 247.94 Earth years, meaning Pluto will not finish its first full orbit since its discovery until 2178.
New Horizons made its closest approach to Pluto on the 14th of July 2015, after a 3,462-day journey, and revealed a geologically active world. It found Sputnik Planitia, a 1,000-kilometer-wide basin of nitrogen and carbon monoxide ice whose surface is only about 180,000 years old, as well as evidence of glaciation, possible cryovolcanism, dune fields, and a highly contrastive surface ranging from charcoal black to white and orange. The spacecraft transmitted a total of 50 billion bits of data, with the last bit received on the 25th of October 2016.
Pluto has five known moons: Charon, Styx, Nix, Kerberos, and Hydra. Charon, the largest, has a diameter just over half that of Pluto and was first identified in 1978 by astronomer James Christy. Nix and Hydra were discovered in 2005, Kerberos in 2011, and Styx in 2012. Pluto and Charon are tidally locked to each other and are sometimes described as a binary dwarf planet system because the gravitational center of their orbit lies outside Pluto itself.