What is fbclid? the new facebook parameter

For two days, I have noticed that the URL that I publish on Facebook, there is a parameter is added:
?fbclid=uFCrBkUgEvKg...
To be more precise something like: http://example.com?fbclid=uFCrBkUgEvKg...

Does anyone know what this parameter does?
What is it for and what is the use of the developers?

Thanks for your comments.