The inner planets are called "inner" because they are closer to the Sun than the outer planets.

Here's why they are grouped together:

* Location: They orbit within the asteroid belt, a region of rocky debris separating the inner and outer planets.

* Composition: They are primarily composed of rock and metal, unlike the gas giants (Jupiter, Saturn, Uranus, Neptune).

* Size and Density: They are smaller and denser than the outer planets.

* Atmosphere: They have thin atmospheres, often dominated by carbon dioxide, compared to the thick atmospheres of gas giants.

Let me know if you'd like to learn more about each of these planets!