1. Earth's Orbit: We observe the planets from Earth, which itself orbits the Sun. As Earth moves, its perspective on the other planets changes, making them appear to shift their positions relative to the distant stars. This is similar to how objects outside your car window appear to move as you drive.
2. Planets' Own Orbits: Planets also orbit the Sun, each at their own speed and in their own paths. This means that their positions relative to Earth and the distant stars are constantly changing.
The combination of these two factors creates the apparent motion of planets through the background of stars.
Here's a simple analogy: imagine you're on a merry-go-round. As you spin, the people on the other horses will appear to move relative to the stationary objects surrounding the merry-go-round. Similarly, as Earth moves in its orbit, the planets appear to move relative to the distant stars.
