How are the planets of the solar system often grouped?

Answer 1

The planets are often grouped as the "inner planets" and the "outer planets" or as the "rocky planets" and the "gas giants."

The inner planets are Mercury, Venus, Earth, and Mars.

The outer planets are Saturn, Jupiter, and Uranus. (Pluto was an "outer planets" until it was redefined as a planetoid.

Now that Pluto is not considered to be a planet, the outer planets are the same as the gas giants, and the inner planets are the same as the rocky planets. (Pluto was thought to be a rocky planet, or, at least, not a gas giant.

Answer 2

Mercury, Venus, Earth and Mars are terrestrial planets. Jupiter, Saturn, Neptune and Uranus are gas giants.