A new craze is sweeping playgrounds and schools that could rival the Tamagotchis and yo-yos of years past – Fidget Spinners.

The handheld devices have already been banned for some schools in the UK and US, with teachers taking to social media to vent their annoyance at the toys.

So, what exactly is a Fidget Spinner?

In short, they are small ball-bearing devices that users can rotate between their fingers.

Each Fidget Spinner has three ‘legs’ sticking out from the centre, which is where the user hold the Spinner in order to rotate it.

What’s the point of them?

There’s some muddy waters here. Many Fidget Spinners are being marketed on their ability to help easily distracted children concentrate more, or as a tool for anxiety in the classroom.

Some have even suggested the toys serve as a low budget antidote to attention deficit hyperactivity disorder (ADHD) – however plenty of scientists have already come forward to suggest these claims are likely exaggerated.

[Read more: How well do you know internet slang? Take our quiz and find out]

But are there any scientific benefits?

Given the new nature of Fidget Spinners themselves, there’s no research on these toys that has yet been carried out.

But some have pointed to other research from the Journal of Abnormal Child Psychology, who in 2015 published a study which found that children taking part in gross motor activity (movement of large areas of the body) perform better than those who sit still during tasks.

There have also been multiple reviews from parents of autistic children who have reported their kids enjoying and performing better in school and social situations with classmates when using a Fidget Spinner.

However, it has also been suggested that because using a Fidget Spinner only requires small hand movements they shouldn’t be placed under the umbrella of the 2015 study.

Indeed the author of the report has since said that the bright colours many Spinners come in could in fact be a distraction, and until research is done into the toys themselves it’s impossible to say how much help they offer.

As a result, a host of school bans have started rolling out.

Why are they so popular?

Fidget Spinners appear to have risen in the public consciousness purely through media and online attention in recent months.

Regardless of whether it’s been positive or negative discussion – there are Reddit forums on both sides – it seems that as word has got out, more people have decided to try them out for themselves, much to the apparent frustration of others.

Read more: What is sharenting? Are you sharing to much about your children online