The inner part of the planet can be divided into three different layers: crust, mantle, and core.
The core in the middle of the Earth has slowed down a lot since about 2009. This slowing down makes it look like it's going backward compared to the surface of the Earth.
Scientists study waves from earthquakes to see what's happening inside the Earth. They found that the core might have started spinning the other way after stopping for a bit around 2009.
The core moves like a swing. Every 70 years or so, it changes direction. So, it can look like it's moving backward sometimes.
The inner core is surrounded by a liquid metal outer core, which allows it to spin independently.
Repeated earthquakes and explosions on Earth indicate that the rotation speed of the solid inner core has been constantly degrading.