Example: Jupiter, Saturn, Uranus, and Neptune. The term Jovian came from Jupiter, describing all other gas giants as Jupiter-like. Despite common belief, gas giants are not composed entirely of gas. A rocky core exists somewhere within these balls of gas. Because of the intense high temperatures in the middle of these planets, the rocky core of a gas giant is often liquid heavy compounds, such as Nickel. Thus, it is sometimes misleading when astronomers refer to the rocky core of these planets.Jovian planets are larger than Inner Planets of a Solar System and often have dozens of moons.
So far it is only the Union who activley settles and occupies Gas Giants and not just their moons. The Nul have copied the Floating Refinery concept recently and only about 50 years before joining the Union.
There are several Jovian Planets known to the Union that developed life.