Most objects in the Solar System orbit in a reasonably flat, but not perfectly thin, plane, or disk. Thus, from our view the Moon and planets follow the apparent path of the Sun across the sky. This path we call the ecliptic. Some night when several planets are visible in the sky try tracing your finger through them all, noticing that you are able to do so in a smooth arc, without a lot of moving your arm up and down. That arc traces the thin disk of the solar system. This confined motion of the planets means that they regularly form tight groups in the sky, not only creating a beautiful view but their spread demonstrating they don't quite form a perfectly thin disk. The image here was acquired with a Google Pixel 6 mobile phone shortly after 6:00 am CDT on March 28, 2022. Venus is the bright point-like object above the crescent moon in the trees. Saturn is the fainter dot of light below Venus, about a quarter of the way toward the Moon. The dot of light to the right of the Venus-Saturn-Moon trio is Mars.

In the image below, acquired about 4:00 am CDT on May 15, 2022, Jupiter (left), Mars (center) and Saturn (right) stretch across the morning sky, framed by trees. The flattened disk nature of the solar system leads to these lying nearly in a line, with Mars falling ever so slightly below the line connecting Jupiter and Saturn.