Let me make it easy for you all:
The Killing Fields were a number of sites in Cambodia where large numbers of people were killed and buried by the Khmer Rouge communist regime which ruled Cambodia from 1975 to 1979. Estimates of the number of dead range from 1.5 to 3 million out of a population of nearly 8 million people. The Khmer Rouge judicial process, for minor or political crimes, began with a warning from the Angkar, the government of Cambodia under the regime. More than two warnings resulted in being sent for "re-education", which meant near-certain death. People were often encouraged to confess to Angkar their "pre-revolutionary lifestyles and crimes" (which usually included some kind of free-market activity, or having had contact with some foreign source, such as a U.S. missionary, or international relief or government agency, or contact with any foreigner or with the outside world at all), being told that Angkar would forgive them and "wipe the slate clean." This meant being taken away to places such as Tuol Sleng or Choeung Ek for torture, and/or execution.
The executed were buried in mass graves. In order to save ammunition, the convicted were often executed using only sharpened bamboo sticks. The soldiers who committed the executions were mostly young men or women from peasant families.
The Khmer Rouge regime arrested and eventually executed nearly anyone suspected of connections with the former government or with foreign governments, as well as professionals and intellectuals who were the class targets of the Khmer Rouge. Ethnic Vietnamese, ethnic Chams (who were and are Muslims), Cambodian Christians, and the Buddhist monkhood were the demographic targets of persecution.
The best-known of these sites is Choeung Ek. Today, Choeung Ek is the site of a Buddhist memorial to the terror, and Tuol Sleng has a museum commemorating the genocide. A movie had also been made depicting the events that led to and occurred during this time. The movie title is "The Killing Fields" which was released in 1984, and starring Cambodian actor Haing Ngor. The movie tells of the story of a Cambodian journalist who was captured by the Khmer Rouge and his journey to escape the death camp.
Death toll
The exact number of people who died as a result of the Khmer Rouge's policies is debated. The Vietnamese-installed regime that succeeded the Khmer Rouge claimed that 3.3 million had died. The CIA estimated that between 50,000 and 100,000 people were executed by the Khmer Rouge, but executions represented only a minority of the death toll, which mostly came from starvation. A more accurate estimate of those killed in "The Killing Fields" is closer to 1.7 million executed by the Khmer Rouge and Pol Pot.