In French, they are referred to as “casseurs”, which means people who break stuff.
According to Olivier Cahn who teaches at the University of Clergy Pontoise and is a researcher at the CESDIP-CNRS (the CNRS is the National Center for Scientific Research) there are two types of “casseurs”.
- Firstly you have the “Black Blocs”. They are autonomous and violent groups of ultra-left militants. Their primary purpose is to attack and destroy the symbols of capitalism and the state. One of their favorite targets is the police. For those who are interested, I just came across this book: Who's Afraid of the Black Blocs?: Anarchy in Action, by Francis Dupuis-Déri (it is available in English translation) They are well organized and have well-thought-out tactic. They move around in columns, know how to lift cobblestones off the streets, stock up asphalt in their bags (used to set fire to trash cans etc.) According to Cahn, their techniques were elaborated in Germany in the 80’s.
- The second type is your run-of-the mill thug, mainly from the poorer suburbs. They are just there for the fun of it, are more random. Store windows, cars, trash cans, anything goes as lunch as you can destroy it.
Here are the original French articles from which I have excerpted the information
https://www.nouvelobs.com/politique/reforme-code-travail-el-khomri/20160520.OBS0965/casseurs-la-violence-est-un-mode-d-action-pour-provoquer-le-systeme.html and https://www.lesechos.fr/01/05/2016/lesechos.fr/021893880870_manifestations---qui-sont-vraiment-les--casseurs---.htm
As to the POLICE, despite the MSM’s attempts to debunk the agents provocateurs theory and discredit the claims that they too forment violence which is then pinned on the Gilets Jaunes, as in this article https://observers.france24.com/en/20181204-analysis-rumour-undercover-police-france-yellow-vests
there is raw footage of police-initiated destruction, as witnessed here: “It’s the police that burned the car…I saw it with my own eyes… they were with them and left with them.”
A final note, there are scores of plain clothes police, some with yellow vests on their belts or wearing yellow vest, some disguised as casseurs, even cases of uniformed police with no ID number as required by law.