Which are they?
The Inner planets are Mercury, Venus, Earth and Mars. Theseses are the four planets closest to the Sun.
Terrain
They are made up of rock, however Earth has many different materials on its surface and under the crust. The planets are very desolate, with large canyons and mountains on parts (Earth being an exception). One of them has known life (Mars, obviously). Earth has a very diverse landscape, with most of its surface being covered in Water, and many different climates.
Sattelites
Earth has one moon, moon, Mars has two moons, Phobos and Deimos, Mercury and Venus have no moons. Earth has 2,271 Man-Made Sattelites in orbit.