Black Lives Matter (BLM) is an international activist movement, originating in the African-American community, that campaigns against violence and systemic racism towards black people. BLM regularly holds protests against police killings of black people and broader issues of racial profiling, police brutality, and racial inequality in the United States criminal justice system.
In 2013, the movement began with the use of the hashtag #BlackLivesMatter on social media after the acquittal of George Zimmerman in the shooting death of African-American teen Trayvon Martin. Black Lives Matter became nationally recognized for its street demonstrations following the 2014 deaths of two African Americans: Michael Brown, resulting in protests and unrest in Ferguson, and Eric Garner in New York City.  Since the Ferguson protests, participants in the movement have demonstrated against the deaths of numerous other African Americans by police actions or while in police custody. In the summer of 2015, Black Lives Matter activists became involved in the 2016 United States presidential election. The originators of the hashtag and call to action, Alicia Garza, Patrisse Cullors, and Opal Tometi, expanded their project into a national network of over 30 local chapters between 2014 and 2016. The overall Black Lives Matter movement, however, is a decentralized network and has no formal hierarchy.
There have been many reactions to the Black Lives Matter movement. The U.S. populations perception of Black Lives Matter varies considerably by race. The phrase All Lives Matter sprang up as a response to the Black Lives Matter movement, but has been criticized for dismissing or misunderstanding the message of Black Lives Matter.  Following the shooting of two police officers in Ferguson, the hashtag Blue Lives Matter was created by supporters of the police. Some black civil rights leaders have disagreed with the groups tactics. 
Sheriff David A. Clarke Jr. has accused Black Lives Matter of being