Spinning is the ability of FreeCAD to display a dynamic rotation of the modell without user interaction.
Spinning is by default enabled. To enable or disable spinning go to the Edit→Preferences menu, change to the Display settings and click on Enable animation.
To make a 3D-object spin, rotate it with the mouse and release the mouse buttons before stopping the mouse motion. The object then continues with its rotation.
Another way to put in rotation an object is use Tools -> View turntable... command