They all have a liquid core.
Uranus and Neptune look very similar.
Jupiter, Saturn, Uranus, and Neptune are the gas giants of our solar system.
There are four gas giants in the Solar System - Jupiter, Saturn, Uranus and Neptune. Yet there is probably countless other gas giants out there.
Uranus is pretty similar to Neptune. They are both ice giants, are roughly the same size, occupy the outer solar system (they are notionally next to each other in 'order') and have significant chemical composition similarities.
The first four are all terrestrial planets. The other ones are gas giants.
Jupiter, Saturn, Uranus's, and Neptune.
The ice giants are Uranus and Neptune. Previously they were classified as gas Giants, but since the voyager flypasts it was noted that they has a completely different structure to the other gas giants (Jupiter and Saturn) Whereas Jupiter and Saturn are composed of mainly hydrogen and helium, Neptune and Uranus are composed of a rocky core surrounded by a "slush puppy" solution of ice and methane.
This would refer to the outer planets; the gas giants. In other words, Jupiter, Saturn, Uranus and Neptune.
Well there are actually only two, Jupiter and Saturn. The other two are more properly called Ice Giants and they are Uranus and Neptune.
Earth is a similar size to Venus (Earth is a bit bigger). Neptune and Uranus are also of a similar size.
Jupiter and Saturn are called gas giants. They are composed primarily of hydrogen and helium, with some water in various physical states. Uranus and Neptune are called ice giants. They are composed of heavier elements and less helium and hydrogen than the gas giants.
Neptune's atmosphere, while similar to Jupiter's and Saturn's in that it is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, it contains a higher proportion of "ices" such as water, ammonia and methane. Astronomers sometimes categorize Uranus and Neptune as "ice giants" in order to emphasize these distinctions.