Titan was discovered in 1655 by Dutchman Christiaan Huygens. It orbits Saturn. Huygens named it Luna Saturni. When more moons were discovered, it was re-named Saturn II, then IV, then VI, which stuck as the official title, even though there are at least 19 moons in closer orbit of Saturn. It's also been referred to as "Saturn's ordinary satellite," but Titan is anything but ordinary.
Titan is the only body in the solar system, aside from Earth, with stable liquid bodies at its surface* and a dense atmosphere. Its landscape is relatively smooth, although there are mountains. As on Earth, the air is primarily composed of Nitrogen. Methane and Ethane clouds produce rain, wind and weather that give it seasons. It also has subsurface oceans*.
Embedded video from NASA Jet Propulsion Laboratory California Institute of Technology
The name Titan was chosen by John Herschel in 1847. The Titans, according to the Greek Religion and its adherents, were the former rulers of Greece during the Golden Age. The leader, Kronos, feared that his offspring would attempt to overthrow him, just as he had his father. To prevent this, he ate his children, except Zeus, who was saved and ultimately did overthrow the Titans and banish them to Tartarus.