Lynchings are defined as extra-judicial killings, often, but not always, perpetrated by a mob of more than three people, and in the case of spectacle lynchings witnessed by crowds in their thousands, including women and children. Victims were either hanged or shot; in many instances they were drowned, asphyxiated, beaten to death, tortured, burned alive, stabbed, and/or dismembered. Souvenirs were also collected - shards of rope or the charred remains of teeth, bones, and body parts - and photographs were often taken, sold as postcards, and sent through the US mail.
In the vast majority of cases the victims had been accused of rape or murder, had sought economic or social independence, or had violated the unwritten caste system that appeared after Reconstruction and through the Jim Crow era to the present day. Whatever the perceived offense, the victims were viewed as expendable and the physical threat and actual violence against them facilitated the existing power structure and, in the case of racial terror lynchings in particular, gave explicit agency to white supremacy that still persists to this day.
The perpetrators were almost exclusively European American men, and the culture of impunity ran so deep that very few were ever arrested and tried, and local all-white juries nearly always acquitted those who were brought to trial. Since 1964, however, and the passing of the Civil Rights Act, there has been a significant increase in the number of arrests and convictions.
The Tuskegee Institute has compiled data on 4,743 lynchings between 1882 and 1968 across 42 states (though the actual number is considerably higher: preceding 1882 and occurring much later than 1968. It's very likely that thousands of lynchings and racial murders went unreported, while many victims simply went missing). And while people of various ethnicities and racial backgrounds were killed, including Mexicans, Native Americans, Chinese, and some European Americans, the overwhelming majority were African American victims of racial terror lynchings.