Stars are very far away, to someone on Earth they move as one across the sky like dots on a dome being rotated overhead.
Planets are much closer, they moved in a direction that was different from the stars and could be seen over time doing so. They even at times appear to go “backwards” against the motion of the stars.
“Planet” is itself derived from a Greek word for “wanderer”; this included the moon and sun as well as the visible planets since they also did not move with the stars.
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