A gaggle of protesters dressed in all black, often wearing masks or bandanas to conceal their identities. They’re often on the front lines of loud and violent protests, fighting for their believe of “anti-fascism,” “anti-racism” and “anti-hate.”

This type of tactic is called “black bloc” — it’s an old method of protesting that often leads to chaos. The tactic was used last summer in Sacramento when Antifa (an anti-fascist group) and other protesters clashed with white supremacist and neo-nazi groups at the state Capitol.

It happened again in February when protesters forced UC Berkeley to shut down a speaking event with right-wing commentator Milo Yiannopoulous after a riot broke out.

Now, some locals are worried that the “March Against Sharia [Law]” event planned in Roseville Saturday morning could lead to similar chaos. The rally is one of nearly 30 “March Against Sharia” events across the country hosted by ACT! For America, the self-proclaimed “NRA of national security.”

On the Facebook page, organizers hail the event as being “for human rights” and asks people to join the rally against Sharia Law, an often misinterpreted philosophical law practiced in the Islamic faith and in some Muslim-majority countries.

“Sharia is incompaitble (sic) with our Constitution and with American values. We stand against female genital mutilations and child marriages,” organizers wrote on the event page.

Almost immediately, the Roseville event spurred rivaling protests. One event, the “No Hate! No Fear!” rally organized by the Act Now to Stop War and End Racism Coalition (ANSWER), has prompted some concerns of black bloc-style responses.

In a post on its’ Facebook event page, ANSWER organizers posted, “We stand united against Islamophobia and Fascism. Antifa are welcome.”

Although not every event where Antifa, or similar organizations, are present result in destruction of property or fighting or general chaos, the invite still raises some people’s alarms.

So just what is Antifa? For starters, it’s a organization that represents anti-fascism—hence the name.

The group often uses black bloc tactics such as wearing black clothes, black masks, sometimes black helmets and even shields. Their main objective is direct action against any force that they perceive to have a fascist agenda.

Antifa is one of many organizations that represent a movement of protesters using black bloc tactics. The tactic has come into the forefront of protest during this current political climate, and, although the history isn't clear, it has been around for decades.

An often-cited article written in 2001 by Daniel Dylan Young says that the tactic gained traction in America in the late 1990s and was used in Germany during the 1980s.