Planet or moon?
Definition of a Planet
The
IAU notes the very rapid pace of discovery of bodies within the Solar system over the last decade and so our understanding of the Trans-Neptunian Region is therefore still evolving very rapidly. This is in serious contrast to the situation when Pluto was discovered. As a consequence, The IAU has established a working group to consider the definition of a minimum size for a Planet. Until the report of this Working Group is received, all objects discovered at a distance from the Sun greater than 40 AU will continue to be regarded as part of the Trans-Neptunian population.
(
http://www.iau.org/IAU/FAQ/sedna.html)
Some further reading shows that any mass with less mass than a brown dwarf (which is more of a failed star than a planet) that also goes around a star (is part of a solar system) is considered a planet, regardless of how small. (So a chunk of rock the size ofa fist in a solar orbit is still considered a planet.)
A further distinction is made between
major and
minor planets. The major planets are the 9 (or 8) we all learn in grade school, while the remainder are considered minor planets.
Further complicating the definition is that some moons are actually more strongly attracted by the Sun than the planet they revolve around (example: the Earth's moon, some of the outermost moons of Jupiter, Saturn), so they could also be considered to be double planets sharing the same orbit around the sun. However, this isn't a significant factor in the case of Titan.
Thus by any way you want to slice it, Titan is classifed as a moon, not a planet. On the other hand, it's on the scale of a planet/large moon like ours, so it's appropriate to think of it as another planet you might be able to visit in the far future, if you'd like. I, for one, would like to buy some beachfront property on that methane lake.
Might be a bit cold for Saturn-bathing, though.