Pluto is one of many dwarf planets in our Solar System. It is one of the largest Kuiper belt objects. Due to its distance and faintness, Pluto was a hard target for astronomers to study through conventional telescopes.
Pluto was originally considered to be one of the Solar System's nine main planets when discovered in February 1930, leading to its popularity in 20th century science fiction. However, Pluto was demoted to "dwarf planet" status in August 2006, as astronomers discovered that the Kuiper belt is populated with many other dwarf planets of similar size.
Pluto has 5 known moons: Charon, Nix, Hydra, Kerberos, and Styx. Notably, Charon plays a major role in Mass Effect lore, where the moon is revealed to be a dormant Mass Relay.
New Horizons is a NASA robotic spacecraft launched on January 19th, 2006 which approached Pluto in July 2015, providing our first close observations of the planet.