Source : masterclass.com

Composition Motion blur is a technique that shows movement in both the background and the main object. Many photographers avoid this composition, but not a few also want to get this effect.

With this technique, the resulting photo seems to speak if the object seen is moving when it is photographed. To obtain this effect, the object must be in focus while the background is motion blur.

So you have to move the camera with the movement of the object. Composition is also often referred to as panning. This technique is usually used to create abstract photos, action photos, stage photos and so on.