"Fidget spinners" are small, ball-bearing toy you can make spin using fingers. Acoording to user reviews, the momentum of the toy provides a pleasing experience. You can use it in many ways, even to play your favourite havy metal songs on electric guitar. There is countles youtube videos , how you can use fidget spinners.
Those toys are marketed as aides ADHD, autism and anxiety and cure for problems with concentration.
Psychologists say, that using them can be one of the method for bringing kids' focus back to the lesson at hand.
Fidger Spinner can also teach kids about physics or ball bearing.