Oldest planetary surfaces are heavily cratered. Some planets rotate much more slowly than others. Planetary rotation axes seem to have no preferred orientation to the ecliptic. Planetary atmospheres differ greatly from one to another, especially for the terrestrial planets. Surface of planets and satellites show great variety.
Comets are present at large distances from the sun.
We will refer to these similarities and differences as we talk about individual planets. We'll see how they all begin to fit together as we learn more about the details of the solar system. Collapse in of its own weight. Star, our sun forms in center. Heats up due to increased pressure.