“Black Lives Matter” is a hashtag that grew into a movement, one that resurges on U.S. streets after high-profile deaths of African-Americans at the hands of the police. BLM, as it’s often known, is fueled by history and the power of smartphone videos spread by social media. The most recent trigger for angry protests nationwide was the May 25 death of a Minneapolis man, George Floyd, after being restrained by an officer who was later charged with his murder.

1. Where does the term come from?

In 2013, a neighborhood-watch volunteer in Florida shot and killed an unarmed, black 17-year-old, Trayvon Martin, as he walked to his father’s house from a convenience store where he’d bought iced tea and candy. When the volunteer was acquitted of the killing, an activist in Oakland, California, named Alicia Garza wrote an impassioned Facebook post that ended with “Our lives matter.” It was shared on social media by a friend and fellow activist, Patrisse Cullors, with a twist and a hashtag: #blacklivesmatter.

2. How did it grow?

The term took off a year later, when smartphone images of the deaths of Michael Brown in Ferguson, Missouri, and Eric Garner in New York City, both black men killed by police officers, galvanized the movement. They were followed by protests over deaths caused by the police in Cleveland, Baltimore, Chicago, Cincinnati and other cities.

3. What came before BLM?

Incidents of police brutality have been flash points for demonstrations for decades, including the 1992 beating of black motorist Rodney King in Los Angeles that set off six days of riots and the 1997 torture of Haitian immigrant Abner Louima by officers in the New York borough of Brooklyn. Both episodes resulted in federal prosecutions and convictions of police officers. But before BLM, there was less of a sense of a movement that carried over beyond individual events.

4. How big is the problem?

According to the Washington Post, which has been tracking police shootings since 2015, police killed 1,004 people in 2019, of whom 370 were white, 235 were African-American and 158 were Hispanic (202 were listed as unknown). An advocacy group, Mapping Police Violence, reported similar numbers covering all forms of police killings. The group said that 24% of those killed by police in 2019 were black Americans, who make up only 13% of the population. It also found that 99% of officers involved in a death between 2013-2019 were not charged.

5. What has BLM called for?

The decentralized movement has no formal agenda but protesters have pushed for policies to increase accountability and reduce deadly encounters between police and African-Americans. These included calls for officers to wear bodycams that document the events leading up to and during shootings; the end of military-style equipment like riot gear, assault weapons and armored personnel carriers being used by municipal forces; transfer of police department oversight to local community boards; and legislation to address court rulings that activists say make it all but impossible to sue officers for acts performed in the line of duty. In the latest protests, there have also been calls to cut budgets for police departments.

6. Did any of that happen?

The use of bodycams has been widely adopted, including in New York and Los Angeles. President Barack Obama’s Justice Department conducted dozens of investigations into whether police violated the civil rights of minorities, reaching so-called consent decrees overseen by federal courts that mandated changes in some local police departments. Obama also restricted the sale of military equipment to law enforcement. Under President Donald Trump, the Justice Department has largely dismantled those police oversight initiatives and curbed the use of consent decrees. The Justice Department has also curtailed wide-ranging “patterns and practices” investigations of local police departments, arguing they harmed police morale and were an inappropriate use of federal power.

7. What other opposition has there been to BLM?

In the movement’s early years, some law enforcement groups called BLM responsible for rioting and anti-police violence. A counter-movement known as Blue Lives Matter advocated that those convicted of killing law enforcement officers should be sentenced under hate crime laws. Some critics turned to the hashtag #alllivesmatter, leading BLM supporters to respond that they weren’t seeking special treatment for African-Americans, just equal treatment. Some white nationalist groups promoted #whitelivesmatter. While running for president in 2016, Trump called BLM “very divisive.”