Stellar parallax is the apparent shift of closer stars against more distant stars due to the orbiting motion of Earth. Negative parallax, or stars going the wrong way— occurs due to measurement errors placing the nearer star as the farther one and vice versa.
Stellar parallax directly proves Earths’ motion around the sun, and flat-Earthers use negative parallaxes to dismiss it. In reality, negative parallaxes are just statistical uncertainties.