If you go outside at night and watch the sky for a moment, it looks fixed, eternal. But if you wait even a few minutes, you see subtle changes. Perhaps a meteor will flash, or a human-made satellite will roll by. A few more minutes and you’ll see the stars have moved to the west, a reflection of the Earth’s rotation.
Go out night after night and you’ll see more changes. The planets slowly slide against the background stars as they (and we!) orbit the Sun. The Moon will appear in a different spot (and in a different phase) every night, and if you’re lucky, a comet might be bright enough to see as well.